Question(s) about macros in functions

Hi! I'm know a bit about datapack creation and functions, but am unsure on how the new function macros work, as I'm trying to use them in a datapack that I'm working on What I'm wondering mainly is: - Is there a way to do a sort of "if-then" system within functions with macros? Could the logic work something like this: if (var=1) then kill @e - This may be a stupid question, but do the variables in function macros get stored permanently? So when the server stops and then starts again, will the variables be the same as what they were previously set to? - Somewhat unrelated, but is there a way to change what armor zombies (as an example) can spawn with if (for example) var=1? My idea is to be able to set this variable to "1" when the player gets a certain advancement, and then from that point on, zombies (for example) would spawn with different gear. I apologize if what I asked is unclear, lmk if I should explain it differently.