What is the base value of various 'Fortify' potions and enchantments?

I am playing Skyrim SE with most graphical/texture/ENB mods (on Linux) and Vokrii for talents.

I would like to reinforce my enchanting by crafting potions of Fortify Enchanting and now I managed to get +60% combined Fortify Alchemy gear (15% a piece).

When I try to craft such potion, it goes from 4% without gear, to 7%.
Is the base value of this potion 4%?

Where can I find such base values?
I guess I could use the Fortify Enchanting –> Fortify Alchemy loop for some tries, but how much can I leverage it? Is there an overall cap?

I understand that with Vokrii talents I could level up to 100 Alchemy and get 100% boost (hence I would imagine the base to go 4% –> 8%).

Again, trying to run glitch-less.

Thanks!