Just recently an addon for OMSI was released that may run OMSI better and more stable: https://steamcommunity.com/sharedfiles/filedetails/?id=2461019058 (there's also a version on webdisk but it's less detailed, missing config and instructions)
Originally we looked at it skeptically but now multiple members have tested it and for most it seems to improve OMSI FPS significantly as strange as it is. It is extremely easy to test it out.
As the author also noted on the download page: On the start of OMSI may have micro sttutering (with similar performance or even worse than without this), due to ...