I have an Intel GPU and had difficulties running older Windows applications using old 4:3 display resolutions to scale i.e. fill to screen, a solution is to set the application to run in windowed mode in its own settings (get this to definitely run windowed first), then set the GPU settings to the resolution of the application e.g. 1024 768 then set panel fit to scale in the GPU settings or right click desktop > graphics options for Intel GPU, the application when run will fill and scale the available desktop in a kind of windowed mode, but will often fill to appear to be full screen.