Running two 3070s vs 3080?

Dec 17, 2021
I know this is a dumb question but I'm currently running a evga 3070 ultra and my questions are

1. Can I run a 3070ti with it simultaneously or does it have to be the same 3070?

2. Does it have to be evga brand?

3. What would be the difference in performance running two 3070s vs one 3080?