before you settle on and choose your mech mod, you should look at all the different form factors.
Which includes:
Whether you go for a box shaped mod or a tube shaped mod. The ergonomics and vaping style vary from different shaped boxes to different sized tubes. The build quality and material/metals used also add to the character of the device and ultimately dictate how usable the device will be.
Getting the best from a mech mod requires experience, hence the warnings in the posts above. The more you understand the technicality of using and maintaining a mech mod the better experience you will have using it. Learn the difference between an unregulated mod and a mech mod by researching these forums, there are plenty of threads on it. Mech mods require routine maintenance/cleaning and would also recommend watching YouTube videos on how to clean devices. From techniques using Ketchup or white vinegar/lemon to ultrasonic cleaners, to which metal polish and contact cleaners to use. (Sounds complicated but really isn't)
Once you understand the difference between unregulated and mechanical mods and if your preference is for a mechmod then you then need to think about form factor. single or multiple battery options as well as battery size type. The most popular of which is the 18650.
I also recommend that you should also look up and understand the difference between Parallel and Series mods. Again cross reference a couple of you tube videos and FAQs on this site.
My first mech mod was a straight to battery 510, single piece 18650 copper tube with a solid copper switch and silver plated Spring. I prefer recessed switches as I don't like the hassle of locking rings.
Mech mods can last for life, so would recommend getting the best device in your price range. Clones can be a bit hit or miss, so would stick with authentics to minimise any unknowns.
Of all my mods the safest, easiest to maintain whilst still being a serious performer is the El Diablo Anubis mod. It's 2 x 18650 battery, comes in a variety of funky colours and is small enough to comfortably carry around. It has a 510 pin connection and the internals are copper plated silver to minimise oxidisation. This is a parallel box so 2 batteries will give you improved battery life.
To summarise:
1) understand difference between Unregulated and mech mods
2) study cleaning/maintenance of mech mods
3) understand the difference between a hybrid/ straight to battery and fixed/adjustable 510 pin
4) choose form factor / battery type
5) understand battery safety - search threads on ohm's law
The most important lesson is that mech mods are not as forgiving as regulated devices, you can't stuff them into your pocket with a bunch of keys or change and you need to understand why. They require your attention when using and knowledge of the device to use it safely.
But doing so will allow you to tailor your vape to get the perfomance you seek.