Is it possible to restore apps/data from 4.2.1 to 4.4.4? I'm prepping to upgrade from PA 4.2.1 to CarbonROM 4.4.4 (VZW Galaxy Nexus). I'd prefer using TB to restore my selected apps + data I've had running on 4.2.1, but understand that this is a big jump between Android OSes.

Is there any way to do this? If not both, then what about just the apps?
Generally this shouldn't be a problem. The only problem with restoring between different Android versions is when you backup and restore the system apps' data from a different version. If you only restore the apps you installed and their data, you'll be OK in most cases.

A few apps might have different versions of the app for different Android versions, so those apps might not work properly because you've restored the data from a different version of the app. This is unusual, though, so you'll probably find that all your apps work just fine.