[Help the Newbie?]

Hello PC monsters. I want to join your club soon but as an old gamer could not have time to build a PC for a long time because of the work. Now I want to build a gaming PC but last one was 2006 and so many things have changed. I remember the trouble I had with mini towers back then so I wanted a The Tower 900 for space. Here what I got so far;

Intel Core I9 12900K 3.20GHZ 30MB 1700P CPU
ASUS ROG STRIX Z690 Intel 6400MHz DDR5 LGA1700 EATX Motherboard ROG MAXIMUS Z690 EXTREME
ASUS ROG Strix LC NVIDIA GeForce RTX 3090 Ti OC Edition Gaming Graphics Card (PCIe 4.0, 24GB GDDR6X, HDMI 2.1, DisplayPort 1.4a, Full-coverage Cold Plate, 240mm Radiator, 600mm Tubing, GPU Tweak) ROG-STRIX-LC-RTX3090TI-O24G-GAMING
Thermaltake Tower 900 Snow Edition Tempered Glass Fully Modular E-ATX Vertical Super Tower Chassis

 

And now I need your help with the rest. I want a water cooled powerful PC in the end.

What more I need? Cable, tubing lenghts power supply suggestions I know nothing!

Cheers!