Yes they are. Anything below 150 capacity is defined as small. Anything above 250 is defined as large. That is consistent for nearly all airports dlc workshop planes (and is true for all my workshop planes)

Since the Airports DLC is a dependency, does that mean these planes are properly alligned with the gates, just like the vanilla planes?

That's normal. They will be updated with models that have working propellers but I have to wait for them to be made

The propellers don't rotate, is that a bug or just normal?