If heatsink is hot that mean connection is good.
If you decide to change paste on PCH clean nice him with cotton swabs and Arctic Cleaner.
EK advice for using thermal pad for PCH. I believe that's smart idea and for default cooler, at least 0.5mm if not 1mm it's better.
This is how I Installed thermal pad before block. But I believe that's good choice for any cooler.
Some motherboards have sponge to protect PCH from heatsink. That's sensitive like die on processor and should be careful.
When I removed PCH Heatsink below was some huge thickness of rubberized thermal paste.
I need several minut with cotton swab and actic cleaner to dissolve such rubberized paste. And than I installed MX-4 and thermal pad 1mm over and Monoblock. I just had enough thermal pad rest from VRM. With bigger peace I would cover everything from corner to corner, that would be better.
My PCH go 55-58C on RVE10 when I play games or Benchmark processor.
If Power is on Balanced Mode mostly time is below 50C, now is 47C example.
But X299 is something completely different. VRM is hotter, PCH is hotter, CPU with up to 18 cores.
Monoblock is recommended for X299.