I'm in the process of a upgrading my Cerberus X Threadripper build from an AIO to a closed loop extremely similar to your build. So far I've settled on 2x HWLabs GTS 240 X-FLOW radiators with A12x25 fans on each. I'm happy I went with the X-FLOW version instead of U-FLOW, it should simplify tubing significantly. Here's a quick album if it helps with placement:
I'll be using the same Heatkiller IV Pro CPU waterblock and EVGA Hydro Copper waterblock, so far it looks like the GPU block will fit with a handful of mm to spare. Waiting for a missing bracket before putting the block on my 1080 Ti then I'll get some more pictures. (Also, grab that HC-5599-B1 quick if you can find it, I was lucky to get one on eBay for < $100).
For a pump/res combo I'm going to use a Heatkiller Tube 100 D5 mounted on the front rad's top fan. At stock length I'll need to put my GPU in the third PCI-E slot, which is fine with me since the upper slots will be populated with SSDs and FPGAs. These parts are on their way, I can provide updates images with the pump, res, and waterblocks added. The current plan is to go with soft tubing, but
@fabio has a great hard tube build.
Speaking of
@fabio, he had the same pump/res cut down to fit above the top PCI-E slot, the picture is a few pages back.
I'm planning to keep my Seasonic Prime Ultra 850W Titanium. You won't be able to fit the overhead 120mm fan with an ATX PSU, even at 15mm thin. Based on previous feedback I'm planning to use the PSU fan as exhaust from the motherboard, the front rad as intake, and the bottom rad as exhaust.
Feel free to ping me if you have any questions, I plan on putting together a build guide when I'm done.