ATX 3.0 and 3.1 specs require a different connector for the video card
ATX 3.0 implemented the now infamous 12VHPWR connector
ATX 3.1 "fixed" that connector with the 12V-2x6 connector spec
If you are going to buy a modern video card for your new build, you will want a new PSU which implements the new connector. I recommend getting one that is ATX 3.1 compliant so you don't have to deal with the bad ATX 3.0 connector design
I'm going through this right now trying to get my machine ready to upgrade a 3090 to a 5090 due to recent price drops and MSRP availability on 5090. That's how I found out about all this