I have certain applications set to open in certain spaces, but would like them to open in the background and not switch the space just so I can watch them open.
This will prevent any autoswitching of Spaces, which meets your criteria, but does other things, too, that you may not want:
There is also the '-g' option to 'open' that will run programs in the 'background' in that they won't steal focus away from the current app. Try
for instance. See here for details:
If you want to edit the Info.plist of some application to make this permanent, you can add the key
See here for details.