Don't really know how CSP behaves so can't really comment on that. For all I know it could love AMD cards. In my bit of Googling for it, it doesn't seem to care what GPU vendor you use, but that's just about 5 minutes of searching so take that for what you will.
Not bad, though I'd be trying to go for a 3080, not a 3070 Ti, mostly because the 3080s are actually a bit cheaper. Other than that it's a pretty solid build though
https://uk.pcpartpicker.com/list/nzdftn
Also, I wouldn't hold your breath for Black Friday deals, over the past 2-3 years they haven't really been that great. There's the occasional SSD deal, sometime a PSU deal, and if your lucky a CPU/motherboard deal (though this is usually on last gen gear), but all in the range of ~$20-30 off at most. Not saying you won't find some good deals on those/similar parts, just don't expect a miracle.
It does. The Z690-A Pro is a really solid motherboard, and I can confirm it does have BIOS Flashback (built two different machines with that same board)