0671689 I apologize for the late reply. The monitor will have no bearing on lag or other performance-related issues unless you're playing at a high resolution. 1920x1080 is fine though.
If you'd like help with the game itself, please test with no mods or custom content present, as in, move the Mods folder to the desktop and delete localthumbacache.package.
If that doesn't help, or you don't use mods or cc at all, please provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.