When checking baby gear with other luggage two pieces of baby gear count as 1 of the 2 per person luggage allowance. So someone could check a suitcase, carseat, and say a pack-and-play or stroller as their full luggage allowance.
I have gate checked strollers and I have checked them with other luggage when the connection time is short. I have had to wait for a stroller to come off before and if the connection is tight I just check it.