For some reason, the simulator stopped recognizing my Nvidia GeForce GTX 950m graphics card and runs with the Intel HD integrated graphics (which as you can understand, results in a relatively low framerate). Even if I select "Run with graphics processor → High-performance Nvidia processor", which is the default by the way. I've also tried disabling the Intel HD graphics but then it uses the "Microsoft Basic Render Driver" which runs the game at 6 fps
Normaly the "Run with" option should work. You do have to do that every single time you start the simulator. Have you tried to force it with the Nvidia control panel? You can also try to delete the settings file in the %appdata% folder of the simulator.
The problem with those laptops is that the intel HD is always used to display on your screen. The Nvidia renders the frame, sends it to the Intel and the Intel puts in on your screen.
You can bypass that on an external monitor and some gaming laptops can disable the Intel in the BIOS setting but you need a good amount of knowledge to do so without problems. Otherwise your screen will remain black. With a lot of older games I know the game itself doesn't recognise the external GPU. But as I'm having a laptop with the same confic (Intel HD with GTX 1070 GPU) that can't be the case.