Refresh rate shouldn't have any impact on the frame rate the engine runs at. The actual frame rate you see is limited by your monitor, but the engine could easily run at twice the refresh rate provided you don't have a lot of "clutter" on the screen. If you see nothing at all, then yeah, you could get 180 fps with ease (and I've had this happen). I use 60 Hz refresh rate on my monitor and I've noticed that the frame rate has gotten up to 90 fps when I've got nothing showing up on the screen, except textual panels. Texture quality has almost nothing to do with the frame rate and I've run an experiment (see above) to prove this. The draw rate is intensely high, probably several terapixels or even petapixels per second (a trillion or quadrillion pixels per second) or something. It's hard to test this without having to have high poly models with an oversized skin image.