You have actually managed to squeeze a decoder into the vehicle - I am officially very impressed.
In the larger scales, some model locos do have two motors working off a single decoder (the Heljan OO Garratt for example). My best guess is that as long as the motors and mechanisms are reasonably well matched, you would lose a bit of (potential) fine control but otherwise things would be fine. And seriously, even without DCC, with two or three motor units per train we do get a bit of slipping and lack of synchronisation anyway and yet that doesn't cause any problems. Another important factor for you to consider is the poor pickups on T gauge locos and their vulnerability to dirty track and wheels - even more important for DCC than DC. If you have two power units sharing the same decoder then that means wiring them together and hopefully sharing more pickup wheels which will greatly improve overall reliability. That would more than compensate for any potential sync issues.
As for scenery, assuming that is a serious question
, there are lots of techniques, and it is much the same as in larger scales. Browsing some of the layout threads here would show you several approaches. I personally tend to favour the corrugated cardboard + plaster bandage + paint + scatter process.