What's your main game monitor resolution
I have not had a single crash since the 64-bit patch. I have been playing a little here and there but have spectated a lot of games. And never had a crash ever.
I have also been swapping out hardware for streaming with no crashes. I can adjust sound volume also with no crashes. I have watched full screen and windowed. No crashes.
Monitor 1: 1920x1080 60hz LG 4k monitor
Monitor 2: 1920x1080 60hz Dell Touchscreen
Monitor 3: 1920x1080 60hz Elgato HD60s or $17 USB Video MiiStar capture dongle
GPU: GeForce 1070ti
CPU: i5 - 8400
Ram: 16 GB
Sound: Realtek on board garbage and Behringer UMC404 for short period.
I also recently switched the audio quality in Coh2 from LOW to MEDIUM. No crashes.
I have not tried running 2K or 4K yet since the Elgato is mirrored on the 4k monitor.
EDIT:
I just spectated 3 games in a row on 2560x1440 @ 60 hz with no issues.
Since the 64-bit patch I have seen a couple games that just end abruptly. But I think it is due to my network losing connection for a few seconds.