Yeah this sucks. Returned to SC4 after many years and using the command line below I had no problems. Then I installed network mod and LRM v4 and the screen wont stop tearing. I moved the mods out of the folder but its still happening.
I am running
-intro:off -CustomResolution:enabled -r1920x1080x32 -CPUCount:1 -CPUPriority:high