Im using destruction, alteration, and restoration on an altmer. I will usually carry a paralysis staff for awkward wild fights with wolves, sabre cats, etc. I plan on getting Arch mages robes, apprentice stone, and recovery perks for +250% magic regen

My question is, how much importance should health play when choosing level ups? I've heard of leaving it at anywhere between 100-200, leveling it sparsely

Lol I want to use all magic schools so badly but I know how op doing that is from past experience

I think 250 health would be ideal.

Health isn't going to be as important, and i'd agree with what you've heard, 100-200 health is about right & no rush to get it unless your playing DID/Permadeath.

As to being OP'd, i'd say illusion & conjuration are the two strongest ones, so if you want to avoid that as much as possible then i'd pick one or the other of those two (edit: or neither if you wish) & whichever else schools you want.

On my, non-enchanting, Imperial Battlemage (my only serious main on PC, 150+ hours, no mods) with the Apprentice Stone I put every 3rd or 4th level up into health until I reached 200. The rest went exclusively into magicka. It worked out very well. I used mainly conjuration (sword, summon) and destruction and never felt very OP but I until played until ~45 (Expert).