I have now put together what I want to buy. Does it fit together like this?
MSI B650 GAMING PLUS WIFI AM5 ATX (Retail)
AMD Ryzen 9 7900 12x 3.70GHz So.AM5 BOX
32GB (2x 16GB) G.Skill Flare EXPO X5 schwarz DDR5-6000 DIMM CL32-38-38-96 Dual Kit
750 Watt be quiet! Straight Power 11 Modular 80+ Gold

 

750 watt is too much
500 is more than enough, especially without GPU.

Apart that point ... seems nice.

 

if you plan adding dedicated graphics card later, I'd go for that 750W power supply, not a big deal

 

If you are not in a hurry, it is better to wait for the Ryzen 8000 series that will be released next year. It is predicted that the performance will be significantly improved.

 

yeah for amd you'll want 4 ranks, either 2x16 OR 4x8gb. since it's a high end 7000 cpu i'd go 2 sticks only, either 2x16 or 2x32gb; dunno how 7000 series handles 4 sticks of ddr5. also, the wraith cooler is a gimmick, blows warm air downwards. go with a tower cooler.

 

FYI clean your tower...interior vacuum and as well as the cooler and of course install new thermal paste on the processor..... ;-).