I've never had much difficulty with BG1/2 even in my first playthrough; I rested after each fight, and my party was almost always fully buffed, in full HP, with arsenal of various spells ready.
Replaying the game with BGEE and BG2EE with Roleplaying mindsets, I am restricting myself by not using any buffs before combats and not using meta-knowledge for things like spell choices. (that's why I always memorize at least one protect from petrification.) This adds a bit of unpredictability. However, I feel it is not enough and magic still feels a bit overpowered. I am thinking of resting in each area only once.
The problem is that I don't know if it makes any sense RP wise. In PnP or real life, how often do adventurers rest? Do they refill used spells after each fight? Or do they clear a dungeon without resting? I can justify it with some made up explanations, but I would like to know which way is the most fitting RP wise. Rest after each fight? Rest after x number of fights? Don't rest until you've returned to INN?