Sorry. I was out all day on a local codecamp event.
About the FPS counter, an easy way is to count calls inside the Draw method. And, on the Update method, to control whether a second has passed on the elapsed time, substract 1 second to that variable and reset the auxiliar variable that counts fps. It's not accurate, since after rendering/rasterizing is done on the GPU each frame gets into video memory in general some millisecs later than expected. So the value measured like that would be a proxy.
If you set the framerate to fixed timestep, you will have in average the framerate you target unless you overload the CPU (who counts FPS and make draw calls) so bad, that FPS drops. Now, if you set a variable timestep, you will have the maximun number of FPS count you can get with your videocard, what can be used to measure perf. Take also into account that if you lock the FPS to the monitor's refresh rate, even if you happend to set a higher framerate you will be topped by that.
What's the other thing you need my advice on?