Autodesk workstation & 1440p gaming. Longed to do a P3, it was an absolute dream to build on and made water cooling as easy as possible. If I were to do it again, I'd go with a better motherboard and forgo the colour scheme slightly. The B360M doesn't support RAM above 2666, and I'm not able to OC the 9700K. This isn't a significant issue for me as the system already performs above expectations & my personal requirements.
Testing so far has proved decent temperatures -- GPU 25c/52c | CPU 28c/60c (ambient 21.5c), fan speed around 900RPM is whisper quiet. Credit to the EVGA HC block, it is a fantastic product with all the thermal pads pre-applied. This removed potential for mistakes and ensured the contact between the block and the PCB was perfect.
Mistakes made were: not wiring up the motherboard before piping up the GPU - made it very difficult to do after the GPU was installed. Changed the GPU - CPU connection, reducing number of fittings by one. I also bought too many fittings & didn't end up using the rotary anywhere in the system. My approach was to keep the runs as short as possible & reduce the number of fittings that could cause potential leaks. The EKWB leak testing kit proved to be worth the money spent. Pumping the system up to 0.5bar (50kPa) found a weakened O-ring at the temperature sensor. I replaced it and pressure held at 0.5bar for over 60minutes before removing.