For me, it usually comes down to class systems which has various effects on the games you try it on. I never really felt liked it worked out so well in VII and VIII partially due to how spread out some skills can be in the game so it makes the early sections boring.

Limiting magic in VI was kind of interesting because you never realize how much of a crutch mechanic it is until you make one character a dedicated healer and find yourself in odd situations where you have to actually bother using items since you benched said healer. FFII and XII benefit from a class system the most I feel.

Most challenges I do are hardly challenges and more just me screwing around or just playing the game how I feel the designers meant for it to be. For instance, I usually try to never grind in FFVI and VII and just rush through the game as quickly as I can to maintain a sense of challenge. Likewise in my last playthrough of FFX, I stopped leveling after each character completed their part of the sphere grid. In VIII, I limit myself to one set of 100 for each spell so basically only one set of Fire, Fira, and Firaga instead of everyone having all three, which makes for a much more interesting game. In FFV, I usually ban Freelancer and Mime to make the last stretch of the game more interesting.

In games like Tactics and Tactics Advance I either go all mage/unconventional classes for FFT, or I use the Auto-battle feature to test out how good my builds are. In TA and TA2, I'll make parties composed of one race but different jobs for each.