I have gotten away with some mix and match on 11 speed between them all but once you make the jump to 12 you need to match the link with the chain. Sram/Sram, KMC/KMC, Shimano/Shimano.
You might be able to get away with KMC/Sram mix and match but not guaranteed. Sram also now has "flat top" links that only work on their road bike chains (for now). Shimano 12 speed chains are a dramatic enough difference you have to use their link only.