If I reenlist for a bonus in a Reserve engineer unit, will that bonus be recouped if i transfer to a Reserve DS unit?

I would agree, talk to your career counselor.

Becoming a Drill Sergeant should not require a MOS change, so not sure how that would affect your bonus, it’s just an additional skill identifier.

Current bonuses for Reserve DS. You may not get both but like SGT(P) Jorge Diaz Caro said there’s a certain amount of years you’ll have to fulfill to keep all of it. It’s really be something to ask a career counselor though.

There is a high possibility, however you may be eligible for an affiliation bonus as a Drill Sergeant.