For enchanted armor or rings which would be better in combat?

Use a combination of both, plus the " so and so type of magic is x % less to cast" . Very helpful, and if you love crafting, use alchemy as well.

Magicka regen is reduced to 3% per sec I think while in combat. Go with bigger magicka pool imo, combined with fortify (insert school of magic here) to reduce the cost of them.