If your entire PC is rebooting that’s more indicative of a systemic problem with your system. I’d run a manual full windows update.
id also try to use DDU uninstalled to clean uninstall your video drivers and then reinstall the latest ones
If your card is overheating you can try to mitigate it by enabling vsync. Or getting a much more aggressive fan curve
The systemic problem is W10 and DirectX with AMD drivers.
I had hard hang on two computer since w10 release. One was a 4770k with MSI Rx 470 and MSI motherboard which was working fine on W7 but have issue with W10 (Some window update working better than others). Now, I have a 3400g with MSI mother board which crash. I solved hard hang by setting cTDP at 45W and now when it crash it could have BSOD or GSOD. These crashes now indicate a mix of AMD drivers fault, fault as PAGE FAULT IN NONPAGED AREA , DirectX fault, etc. At least, they are now reported to Microsoft which would perhaps solve them one day.
CK3 is quite unstable, I could sometime plays hours and sometimes it stop in 2mn. I was able to play hours on TWW2 with CTDP at 65W so you could excluded hardware issue and most of the problem occurs after W10 update on my 3400g.