I have a 30" 1920x1200 monitor which I use for gaming. I want to add a secondary monitor to my setup, which won't be used for gaming. I'll use it for non gaming tasks like monitoring system usage while in game or just for more real estate while coding etc. Thus, for this reason and due to space constraints, I'm looking for ~20".
My question is, if I want my display to extend to the second monitor, does it have to be the same resolution as my primary? Because most 20" are 1600x900
Extended Desktop mode can work with any amount of monitors with any type of size or resolution. The second monitor would be blank space which you can drag any window over. This is probably what you want.
There is also Eyefinity or Nvidia surround which works a little differently and does require same resolution screens. Instead of giving you two desktops, it span a single desktop accross both monitors. So when you maximize a window, watch a movie, or play a game it would span across all the screens.