When're you travelling? I'm in the same boat on Jan 24th. Hopefully security measures will return to normal way before that. My advice: if before you fly the new restrictions are still in place, check your bags as if you were flying YYZ-LAS direct, i.e. no carry-ons except small items. Leave the rest in the checked bags. With a tight connection (1 hr usually at YUL) you won't have much time lining up for customs, secondary searches, etc. for you to repack and check your bags at YUL.
GT