If you have a lot of peripherals and need a ton of ports, the Kensington SD5700T Thunderbolt 4 Docking Station is a beast. It has a staggering 11 port...
The new announced Ryzen 9 9950X is should be a good choice for GeForce RTX 4090.
The G.SKILL Trident Z5 Neo RGB Series (AMD Expo) DDR5 is the best choice.