If your curious, you can read up on HDMI here: »
en.wikipedia.org/wiki/HDMIThe article notes that cable length does matter and I suppose so does cable quality; at least to a point. You might want to look at those elements too.
Regarding fitting more windows on the screen, my experience has been that as monitors get larger, so does the window and text unless you increase the resolution. So for the same resolution you won't necessarily get more windows per monitor simply because the monitor is larger. Using two monitors will certainly help.