This is an area where it's really unwise to make too many rules, because the first thing you start running into is the exceptions to those rules.
FW Wintergreen blows TFA's out of the water, strength wise, but TFA's has a better flavor (to me)
FW Marshmallow is the weakest of any of the marshmallows I've used (DIYFS and FA)
I have yet to find a spot where Flv's Cinnamon Crunch is too strong, yet more than 2% of TFA Cinnamon Red Hots would send me howling.
In order of strength, for the brands I've tried, the rough rule, strongest to weakest, is probably: Flv, Inw, FA, WF, Caps/MB/LB, TFA, FW
Trial and error has been the only way I've worked this question out. To add to the quandary, everyone's taste buds are different. I usually mix between 15 and 20 percent, and think I'm one of the few here at VU who mixes that heavy, but even for me there are a few recipes that are fine at 8 or 10 percent.
Your equipment and vaping style will make a difference, too.
Over time you'll get a rough idea of where your mixes end up, for the most part. Say it's around 12%. You see a HIC's recipe that totals 7.5%. In that case, I'd mix the 7.5% with a little room left in the bottle (maybe mix 25ml instead of 30). Give it a few days, depending on what sort of recipe it is, and then taste it. If it tastes wimpy, use the ELR calculator to figure out the difference between 7.5% and, say 9%. If it tastes REALLY wimpy, go to 10%. Add the extra flavors and try again. Keep working it like that until it gets where you want it. If you know that 12% is where you're (mostly) happy, then at 12% you can see where you are with a particular recipe, whether you want to keep working with it or not.
When you let ELR change the percentage on a recipe that's already balanced, unless you get up into the stratosphere, the recipe will stay balanced. Just tweak it until the flavor level is good for you.
I wouldn't go crazy and try to convert a 7.5% recipe to a 25% recipe. No telling what that would taste like, and you'd probably just be wasting your supplies. It is true with a lot of flavors that, past a certain point, they go mute or the flavor changes entirely, and you pick up chemical and other notes you wouldn't taste at lower levels.
ETA: Added
@wildgypsy70 's additions Inw, WF, MB, LB to the strongest-to-weakest list. Thanks ladybug!