I think this is a great motherboard, to have 64gb memory. to save even more space/help with cable management you could use an m.2 drive, and a few 2.5inch saa drives.

You can pick cases like the NFC S4 MINI ~5L (requires an external power brick and only deliveres a max of 400w power) Lian Li PCQ21 ~8.5L, lowest price but gpu length restrictions, plus space for a slim optical drive if you want one. Dan case A4 SFX ~7.5L if you absolutely want a full length gpu.

If you dont need the cpu horsepower, Go with something low end like the 7800k and cool it with the NOCTUA NHL9I or any low profile cpu cooler. The X299 platform is great for a wide range of CPU skus from 4c4t to 18c36t. Upgradable in the future.

For GPU up to you, Just check compatibility with the case.