Ali,
I have never had a problem with trollies at MCO, not sure where that has come from.
Also, regarding luggage, you should be transferred by electric cart at MCO and it has its own run through secondary security and the porter should sort out your luggae.
Best to talk to Virgin Special assistance, they would have more knowledge.
I have never flown MYT, but I think they use Airbus?
In that case, yes they are smaller than a 747 and the roof line is lower than a 747 (more rounded as well)