"OK, so basically the track has to be a Midi track to add certain plugins?"
yes it's different to REAPER, yes sus out that ReWire VST, it is suppose to be implemented soon in RB & BB but who knows when ??

"Haven't been able to add anything to RealTracks."
are you using the Direct Input RealTracks with Amplitube ?

"When I add EZDrummer to an empty track and bang on the drums or something, I only hear music out of one side of my headphone - is this normal or am I overlooking something?"

You can get those little ear syringes from the drug store, it might be just 1 ear that is blocked, lol no, not sure what is happening there, is it just the drums or all coming through on 1 channel, it's not panned in EZD mixer, the midi track is not panned, headphones working ok on other apps ?