I'm not sure if all of you know this, but during combat, your magicka regenerates more slowly and so I'm not sure if it's more useful to have a huge magicka pool or large amounts of magicka regeneration.

I'm going for the 0 cost destruction and along with those enchantments, I can choose to put increase magicka regen or fortify magicka.

What would be more beneficial, considering the fact that I will not be using magicka for destruction spells, but only for conjuration and alteration?

More magic more benefit. Regeneration is directly related to how much magic you have, the larger the pool the faster it regens. So more magic gives you both