Can you fit luggage onto a 2 wheel machine rather then one of the 3 wheelers?
Sure. As with uprights, how easily depends on the bike. An expedition tourer will have ample luggage capabilities, while a racing machine won't.
'Banana' bags can be hung under the seat of a recumbent instead of or in addition to the use of luggage racks, and some bikes have room for a bag attached to the back of the seat.
Streetmachine with a traditional 4 Ortlieb roll-tops:
Secondly can you tow a trailer?
Sure, as long as there's a sensible way to attach it - seatpost mounting isn't likely to work. Rear axle mounting is fine, unless perhaps it's a lightweight racer with dropouts made of fairy farts. Tricycles and single-wheel trailers can be a bit iffy, as trikes don't lean like bicycles do, but two-wheel trailers are fine.
ICE Sprint towing a Carry Freedom Y-Frame: