PC game using mobile renderer

I’m trying to get high FPS on a basic map on a machine with an intel integrated gpu.

Having a look at:

Can I just load a map using the mobile renderer without streaming the level?

How would I hook up the custom “IsInMobilePreview” node to event begin play?

How do I create the “IsInMobilePreview” function, create function then just drop in the code?

Additionally in my version of ue4.15, I already have an “OpenGL ES3.1 Experimental” option in project settings >> platforms >> Windows >> Targeted RHIs, do I still need to amend “GenericWindowsTargetPlatform.h” and “WindowsTargetSettingsDetails.cpp” and “WindowsD3D11Device.cpp”?

In any case where are these files located?