maybe i should try that 4GB patch thing
Yes the CFF Explorer 4GB patch makes a big difference, plus I use game booster 3.4 as well. I also make sure my power settings are at "High Performance"., many PC's and especially Laptops are set at "Balanced" to manage power consumption economically.
Your settings will make a difference. and also which Map you play, some maps are heavier than others. for example I can run Hafen city at full graphics without much problem. lowest frame rate is around 17 fps in certain areas of the map, with an average of 25 to 30 fps on the rest of the map.
I also reduce the number of AI buses on some maps and lower the schedule setting, and of course the amount of AI traffic.
OMSI is all about the settings dependant on the map, but is the only true, good and best bus simulator out there at the moment.
I use a Samsung Chrome laptop with an i5, 2.6 ghz with in built Samsung turbo boost to 3.2 ghz when on "high Performance", 8GB Ram, 64 bit operating system, AMD Radeon Graphics with in built 4GB memory.