(Advice) graphic stuttering overheating 100% GPU

Hi

Just asking for advice

So me and my brother are playing PoE... both of us own RX470 GPU.

my brother PC:
ryzen 7 5600x
Asus RX 470 4gb
16gb ram 3200mhz

my PC:
ryzen 5 3600
MSI RX 470 4gb
32gb ram 3200mhz

The problem is my graphic card is almost IDLE in PoE... it works 90% of the time with passive cooling with no fans running. Its running 75FPS smooth and fine. And my brother GPU is working on 100% load all the time with stuttering and graphic lags.

Cpu's are working fine. for him is 10% and for me 30-40%.
Ram is not an issue.
We both have the same graphic options in PoE either with vsync or with fps cap.

So the actual question:

WHY my comp is running PoE amazingly fine and my brother has problems?
Should we look for problems in PoE or rather in his graphic card?
All other games are running just fine on his GPU...

Im at loss here and dunno what to do.

Oh and we both have amazingly big cooling cases with lots of fans ^^ so the cooling shouldnt be a issue.

Plz help with what we can try next? i dunno what to do with him anymore.

i figured out why lof of poe players have this stuttering issue when in hideout
not even related to engine multithreading. but it helps when disabling it whyle being in hideout. but when actualy killing mobs i reccomend to enable it.

but i wont reveal what or how i got ridd of that suttering :P its ggg job to resolve that not mine. same issue is going to presist in poe 2 too. i cant wait lol

either of you got a free sync able monitor? maybe it's enabled on one computer and not on the other one.