Well, I'm using
I9 9900K OCed
4x8GB ram OCed
2 GTX 1080 TI OC edition with 120% power limit and 100 Mhz OC.
1 14 TB HDD
1 Optane Memory
1 950 Pro
1 1 TB HDD
6 case fan for water cooling
1 3.2W DDC pump for my custom water loop
When playing shadow of tomb raider the GPU usage is 100% for both GPUs and around 40% CPU usage. The average power usage is less than 700W (I'm using a TP Link outlet with build in power meter that I can see in the App, I'm not sure how accurate they are). I would say 1200W is enough. I have a 1600W Platinum tho.