Maybe I misunderstood, do you all have two graphics cards?
Sometimes a PC will have a graphics display included on the motherboard. Many laptops will have this feature (for space reasons). My PC motherboard has no graphics display, so I have a graphics card which fits into a slot on the motherboard.
This gives me the opportunity to upgrade the graphics card if I feel it's too slow, or if it becomes faulty.
If you computer has two graphics systems ("onboard" and "plug-in") it's important to disable one (usually the onboard one) and make sure that the graphics are handled by the more powerful one.
Lewisner has given his PC specifications below the actual post, and his motherboard (like mine) uses a plug-in graphics card, so there's only one.
I have an nVidia graphics card and nVidia provide a control panel where one can select a number of options either for the system, or for a particular program. For my system, my monitor has a 60Hz refresh rate, so I have limited the graphics card to about 75frames/second - there's no point in making the GPU work harder. I can also let Trainz 22 program have "maximum power" so that it can process all the scenery items and consists in Trainz as fast as possible (some routes have lots of scenery and this can slow the output video.).
HTH
Colin