I wanted the same thing, so I set up mine with the 7” touchscreen and case mounted on my frame. I installed raspbian desktop on my pi, and then installed webcontrol that way. I do think that using the pre-made image and then downloading the desktop would be a bit simpler. (My post showing my setup: Calibration Woes - #22 by Spenc )
As far as the usability, I have not had any noticeable issues as far as cpu usage goes. However, I configured mine to run in kiosk mode on start-up and not load the entire desktop, and removed several packages and such that come pre-installed with the desktop image. I added commands in webcontrol to shut down the pi so I’m not pulling the plug every time. I’ve not seen my cpu usage in the webcontrol monitor go over 65% so I haven’t fully taxed it out.
Usability wise, you need a keyboard to make any changes. I like the touchscreen, but I have no way to type. This is an issue if I wanted to move an axis a set amount. I have found that it is mainly good just as a process monitor for now.
If your phone is connected to the same network as your pi, you can open webcontrol on your phones browser (same address you’d use to access from your computer). This is super hand for re-zeroing the z axis, and making quick adjustments without running inside to get my laptop.