[2023] Good PC, Poor Performance

From what you say, probably, yes. But try a few things:

Right click on eu4.exe , properties, compatibility. Tick "disable fullScreen optimisations" untick every other box in that dialog, Apply and exit.

Edit that settings.txt to say:

refreshRate=60
fullScreen=yes
borderless=no

vsync=no

Then in the launcher Game Settings menu, select fullScreen display mode.


IF that doesn't help:
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.

Please attach here your Documents/Paradox Interactive/Europa Universalis IV/settings.txt and pdx_settings.txt .
From your Documents/Paradox Interactive/Europa Universalis IV/logs/ folder, attach here system.log , error.log .  

I see your monitor's native res is 3840 x 1080 - can you try that in the game please?

If no better, try 1920x1080 , which was I think the best res in existence when this game was written.