Are you trying to find out what you are getting in Realflight?

If so FPS is in the navguide.

Edit the displayed widget list via the menu to include the FPS readout.

Then go back to the sim and hit "1" to activate the navguide and see the FPS readout among other things.

Realflight does best in full screen exclusive mode.

Some WIn8.1 systems have problems letting DX9 programs switch to full screen mode.

This is more a function of the installed drivers, available memory and video graphics system capabilities.

The better the hardware the better the results.

That said I have Realflight 6 & 7 running just fine and decent FPS numbers to boot on a laptop system with an HD4000 Integrated chipset and a high end Nvidia GPU.

I've used Realflight without noticing that I did not enable the Nvidia GPU at all and I was utilizing the HD4000 alone.