You should bolt the psu to the frame, or at a minimum run a wire from the psu to the frame as that's the grounding path for anything attached to the frame, it's also the grounding path from any RF (radio frequency) or other sorts of EMI (electro-magnetic interference). Those 4 little screws in the back of the psu have quite an important job.
You changed the psu. I've yet to see a cpu/eps cable not long enough to reach except in full towers with a standard ATX psu, or using an SFX psu in a mATX or larger case (small form factor psu). So not sure exactly what's going on there, but the best fix is a cheap extension cable for cpu/eps and bolt the psu down as needed and still reach the EPS via routing around the back.
As far as temps go, hopefully when you swapped out the psu, you also replaced all the cables, and did not use the old ones. Check every cable, every connection.
With water coolers, if they are working correctly, there will be No discernable heat difference between the tubes, there is a difference, it's generally 1-3°C, but ppl's fingers are not sensitive enough to discern that small amount. If you think that it's a cooler problem, hold your hand next to the radiator exhaust, it should be warm and the fan spinning at a high rpm.
There's 2 kinds of liquid cooler types. Simple and complex. Simple has a single cable with 3-4 wires that attaches to the motherboard coming from the pump. It may or may not also have fan wires at the pump too. Complex uses a single wire to the motherboard, but requires psu (molex or Sata) power cable, generally has fan cables and almost always a USB cable, for software control.
If the fan barely spins, or doesn't get faster with loads, that's either a bios setting issue, a software setting issue or for some reason the plug got put on the motherboard wrong/off a pin.
If there's no real heat coming from the radiator exhaust, that could be a pump issue, software issue, paste issue, mount issue or power issue, like you missed plugging the complex pump back to the psu after the swap.
Honestly, you'll need to physically chase every move you made during that swap, make sure everything that should be plugged in, is plugged in, correctly, using the new cables. After physical inspection, then you can start in on software or bios settings, but that's going to require you know where the fan/s and pump are plugged in and checking for function