Thanks for helping so much.
I loved my 3100 to bits for being so economical. Maybe I'll just dig it out of my drawer, pop it back into the mobo and call it a day.
I'm sure it would be plenty powerful for the low profile GTX 1650 I bought for it.
Speaking of cases, I bought this one originally for a HTPC, but I thought why not use it as my main PC as it has a huge grate on its side for CPU air intake. It always had the 3100 running around 45-50 degrees with the tiny Wraith Stealth even at full load. Maybe that grate doesn't help with the 3600 as much as I thought.
Other thing: I managed to find the PPT setting in the BIOS. With it set to 65 W, PBO enabled, the CPU runs at the low 70s under a Cinebench run. Weird thing that now HWinfo reports clocks between 4-4.1 GHz, while Windows Task Manager got stuck at 3.6 GHz. Idle clock reporting is also all over the place.