@duraturk - You seem to be well on your way. I honestly don’t think the monitor quality matters all that much for a normal Magic Mirror installation. And by “normal” I mean “using the standard white-on-black interface to display text” installation. Compliments, calendar, weather, newsfeed, plus some sort of transit schedule.
You might notice a difference in monitor quality if you plan on watching full screen video or high resolution photos of the Earth or some such. But I doubt it.
As for the size of the glass vs the size of your monitor, I think you have it right. The barely-bigger-than size will do just fine. Push comes to shove, you can remove the bezel from the monitor to reduce its size a little bit. Additionally, with a close fit you won’t have to worry about suspending or supporting your monitor behind the glass outside of the regular box that is the normal design. The “other components and cables” usually fit behind the monitor in the various gaps left by a flat wall up against a decidedly non-flat monitor case. In my experience, the depth necessary just to accommodate the monitor electronics is more than enough to fit the Pi and the power source.
I have shopped with TwoWayMirrors before and they provided excellent service.
