A long post but you seem similar to me, what I enjoy and what I experienced when I started.
Just my opinions of course and I am relatively new at all of this but I have learned fast.
If you get a drink and settle down and slog through it hopefully it might shorten your initial learning curve a bit.
I am a menthol lover too, started smoking Newports for a few years and eventually switched to Kool milds for decades then at the end got into L&M Menthol because they were cheaper.
I smoked for 40 years and tried the gas station e-cigs a few years ago but they didn't take.
Then in Feb. of this year I walked into one of the local Vape shops around here.
I bought a bottom line Joytech D16 which was recommended on me to get started, also a small bottle of some in-house mixed Newport juice, (that I later found out was mismarked and actually was a straight menthol mix), at 6mg and that did it...I finished off the few cigarettes I had left in my pack and didn't buy another.
It was great, close enough to that cigarette experience and I was happy.
Not long after I decided to treat myself to an upgrade so I did my research and bought a Aspire Zelos kit with the Nautilus 2 tank.
Now we were talking...options for power adjustment, draw and several coils from sub ohm to higher.
Still into MTL, big clouds never interested me but flavors did so I got an extra Nautilus Mini tank so I could share coils and switch flavors around when I want to without emptying tanks.
Not long after I got into mixing my own DIY juices and after buying my first rebuildable dripping atomizer I started building simple coils.
DIY juice is easy to mix and coils are not hard to learn to do and the money savings are tremendous...especially in the juice department but I still treat myself to commercial juice when I can catch some at good prices.
I think if you are actually doing DTL, direct to lung, you might want to practice getting good at mouth to lung...pull into your mouth, inhale and then exhale just like a cigarette.
This is the true cigarette smoking experience where you can get vapor, flavor plus that throat hit, (with the right settings and juice), which is what most smokers crave.
Since you seem like you are like me, you enjoy menthol and prefer the MTL experience, here are a few of my current combinations, settings, coils and juices I enjoy or have enjoyed in the past.
Juice
I have tried some Halo juices, Kringles Curse is nice although more peppermint than menthol.
I bought some at a super sale, ($5 for 50ml), a bit higher 12mg nic level than the 3 or 6 I usually vape but what a great throat hit and I like the minty taste.
At that price I couldn't resist buying a ton and I learned the 12mg nic is great for getting my nicotine and I don't have to Vape as much as I do with the lower nic levels.
I skipped over 12 completely when I started at 6mg nic but for when I want my "cigarette smoke experience" I think I will stay at 12mg...you are always learning in this biz.
Yeti juice is similar if you like peppermint but Halo is better tasting, to me.
As far as commercial juice that approximates the cigarettes I used to smoke extremely close juice is going to be Halo Menthol Ice.
It is the bomb, I took a trip to New York for few days, ($12 a cigarette pack or more there), and decided to treat myself to some new juice and fell in love.
Does the job in my AIO and in my Zelos and either the Nautilus 2 or Nautilus Mini mini tank the experience is stellar...at really low wattage too.
Despite the good flavors and nice bottles from these commercial companies what I use the most is my own tobacco/menthol mixes which cost me pennies per ml and is just as enjoyable to me if not more.
For commercial nontobacco/menthol flavored juice one I really enjoy is Tailored House Strawberry Crunch but like most commercial juices can be pricy if bought at B&M shops so I found a great recipe online that is extremely close and just mix it up myself most of the time.
As far as he equipment I find it astounding that you started vaping doing DTL and at the wattages you stated.
Your AIO is lower wattage but that Coolfire is way more powerful.
I do the higher wattage thing too, I got that Legend and all the other mods that will go from 50 watts on the Zelos way up to over 200 watts but it is a rare day that I ever go any higher than 40-70 watts on anything on any of my flavored juices.
Those menthol mixes and commercial peppermint or menthol juices, well, those are all vaped at very low wattage, going high they won't feel like cigarette smoking at all to me and would probably kill my throat like big time if I did them at higher wattage too much.
I tried to read all your posts about what juices you are trying, the wattages you are playing with and the equipment you are using and I might be wrong but it seems like you are still searching for that cigarette experience, that perfect menthol light MTL experience you got from cigarettes.
That's normal, this is a journey and eventually you get it all dialed in as long as you keep trying and don't quit.
Your perfect vape is out there, you will find it soon enough.
Here are some of my best suggestions to hopefully get you there a little quicker, or at least the things that worked best for me.
You got a good mod, here are the tanks I own that I bought specifically for the best flavor and cigarette MTL experience...also I use low wattage and battery life is tremendous when you do it this way, even on my Zelos internal battery unit.
The Aspire Nautilus 2 or its close cousin the Nautilus Mini with .7 ohm coils.
I have used the higher ohm coils, even a Clapton coil but the closest I get to the feel of a cigarette is that .7 that I usually Vape at about 13-17 watts.
Great flavor on my flavored juices too but I usually use those in my higher wattage setups...for the best, closest cigarette experience find the menthol juice you like and set it up in one of these things.
These atomizers are usually mounted on my Zelos, I never come close to 50 watts on that thing and at below 20 it lasts all day.
This has actually been the one I take with me when I leave the house lately because it is a richer and more adjustable Vape than that AIO.
Over both of those my favorite MTL atty is actually my Ares tank.
You were looking at the kit with the Zenith tank early on in this thread, this tank was designed by the same two guys except the Zenith tank uses store bought coils where on this one you can easily build and install your own coils and really dial in that Vape the way you want.
It comes with wire, cotton and tools that you can use to build your own coils in the box because these guys are huge into MTL and put these tank kits out to specifically get people off smoking as simple and easy as possible.
I have used this thing on all of my mods but it has found a home on my newest acquisition the Fuchai 213 mod for a few reasons.
That mod is a squonker but it only has one battery and the only one I have for it now is an 18650.
It can use bigger batteries and I assume it will last longer at higher wattage once I get one but that 18650 doesn't last long at at 40-50 watts or higher.
I am just getting into squonking but I think I will look around for a better 2 battery squonking mod for that purpose.
This mod, however, works extremely well with my Ares tank set at between 14-18 watts on the 1.24 ohm small Clapton coil I threw in there.
The battery lasts and lasts and the flavor, throat hit and menthol cigarette experience is as close as I have gotten with any combination of mods and atomizer I have tried so far.
On this one I do primer puffs, (a small short puff before I take my main puff), and that way with your eyes closed it is hard to tell this is not a cigarette I am huffing on.
Especially with my own custom recipe tobacco/menthol juice loaded up in it.
It took a few months to get to this level of my own journey and I am not done yet but that journey has been incredible all along the way.
I now enjoy vaping more than I ever enjoyed smoking, I have saved a ton of money and even learned a few new skills along the way and the learning will never end.
If you ever want to get into mixing juice there are a ton of posts, recipes, and vids out there to help you get started.
Supplies are actually cheap and you don't need major skills or a ton of supplies or flavors to mix up some pretty tasty and satisfying juice....cheap!
Making your own coils...there are some very talented coil guys that have learned to make some exotic, beautiful and extremely flavorful coils out there but if you get into a rebuildable tank like the Ares or any other tanks, squonkers or drippers where you can put in prebuilt coils or your own and building simple coils is, well....simple.
Get a little bit of cheap wire, wind it, clip it and insert it into your atomizer.
Like most everything in life you can make it as complicated or as easy as you want it to be.
Those simple round wire builds...they can still work extremely well.
Again, plenty of help and a million tutorials and vids out there if you ever want to try it.
No matter what keep on trying, experimenting and moving along your journey until you get to where you want to be...and then go further if it suits you.
Quitting the stinkies, saving money, living a more healthy lifestyle and an ultimately longer life is the goal.
If you find you are enjoying yourself and having fun along the way then welcome to the club, most that are on this forum will tell you that is a great bonus and reward we have all discovered on our own journeys.