First of all, welcome to the community! Secondly, I’ll give you a piece of advice that I’ve given to every single newcomer to the system who wants to tinker and modify the system without any experience: Don’t.
Most of the time it’s a bad idea because you lack the necessary experience to make informed decisions on how to implement these ideas properly since you don’t know how the system is supposed to run normally.
So maybe try running at least a couple of test-sessions first before jumping straight into the homebrew territory.
It matters a great deal, actually. Mana in Magic: the Gathering is very different from mana in Zelda games which is very different from mana in the Black & White series. So the more information you can provide, the easier it is for us to recommend something. For example, I could point you to my (WIP) Spellcasting for High-Fantasy settings but it requires some reworking for a Zelda setting.
Again, you’ll need to be more specific with what you mean when you say “Stamina” since Open Legend’s Hit Points are quite interchangeable with the word Stamina. What aspects of HP don’t meet your criteria of being Stamina? And what is Stamina supposed to accomplish in your world that HP currently isn’t?