I have two gaming pcs. How do I choose the right UPS?


Beta member
So I need to buy a UPS/No-break to hook up my 2 gamings pcs. I don't plan on upgrading any internal components, ever. So here are my questions:
1: I thought all I had to do was add the Watts of my two pcs's power supplies, and then get a UPS with the same or higher capacity. Am I right, or there's more to it than just that?
2: Do I only take in consideration the watts of the 2 power supplies? Because if the power supplies can handle the pcs workloads, the UPS just needs to handle the power supplies right?
3: If the pc draws more power than the ps can supply, will the ps then draw more power from the UPS? Or does the ps act as a barrier, and doesn't let the pc draw more power than the ps can supply?

I know it's a lot but I can't find the anwsers anywhwere!