my UPSes are only used to allow for safe shutdown of the servers they’re attached to, so 10 to 20 minutes is ample time.

For “offgrid” or power-outage computing I use solar with Jackery batteries to power my essential networking equipment and a couple mini-PCs and my and my spouses laptops.

I haven’t found any AM4 motherboards besides ASUS boards that support bifurcation (confirmed in documentation, at least) and even the ASUS boards don’t support 4x4 bifurcation.

As long as you can confirm that whatever motherboard you pick will support the bifurcation you need, you should be good (and I’d be interested to know if you do happen to find one, for my own server).