A while back a new Windows 10 update seemed to cause a problem with this game. Basically, my computer is top notch and could play the game fine, then one day I noticed that it was stuttering and lagging like fuck. The only thing that had changed on the system was the fact I'd installed a major Windows 10 update (I think it was version 1709, AKA the 2017 Fall Creators Update) so I assume it had something to do with that. I eventually found someone mention this fix in the community forums (so kudos to whoever that was, as I can no longer find their post to link to it).
Find the executable for the game called
RelicCOH.exe, by default it's in
C:\Program Files (x86)\Steam\steamapps\common\Company of Heroes Relaunch but it will be wherever you either have Steam installed or wherever you install your Steam games if not in the default location. There's another executable in there called
RelicCOHO.exe but you can ignore that one. Right-Click on the executable, select
Properties at the bottom of the menu, select the
Compatibility tab and then put a tick in the box for
Disable full-screen optimisations. Run the game and you should no longer have a stuttering, laggy pile of shit. While you're at it, you can also add the
-nomovies command line switch (on Steam you do that by setting launch options in the game's properties) to get rid of all those annoying intro movies when you start the game. You're welcome.