The best I can measure the internal psu temp, with an infra red laser temp device, the hottest thing in my PSU is a coil at 42C when the system is under load.
Imo all current PC PSU's whatever make, are generally pretty poor by design and in general build. I have a PC power & cooling 600 watt PSU here and even that looks shoddy in the component layout and build. Until there is a real demand for a fanless PSU of quality construction with high power output ratings without the heat issues, they will keep making the current cheep & inefficient designs. The fanless ones that are availble now are usually low watt rated, and or will get too hot anyway with a hi performance PC.
There are things in a PSU that get hot once the main items are cooled effectively, especially when the forced airflow is totally removed. This is why I made my design partly cool the transformer in the block mounting. The other thing I had to do was thin out the wiring inside and make a bracket to the block to help cool a coil that was getting far too hot under load 70+C
Water-cooling a PSU is a much more complex thing than any other part of the system mainly because they are not designed for zero airflow. zero airflow is a world apart from just a fan near it at 5v. Mines almost a year old but it could still die tomorrow for all I know. I've done the best I can and as far as I can tell nothing is getting overly hot now, but some small part might be..... leading to a reduced service life.
At the end of the day I'd much rather have gone out and bought a much higher quality PC PSU that was designed from the outset to be fanless, powerful and cool, even if it were 4x or 5x as expensive, but as there isn't anything available, the only solution left was to work on what I had towards my zero fan silence with performance goal.
