Looked at a 38A yesterday

[RKNOLA]

I don't know about the changes to the 2018 but no the slide toppers didn't come with covers on ours. Our 2016 38A did have a DVD player/drop down screen under each bunk, but the 2017s came with a bigger screen and DVD player. I am not sure what the 2018s will have.
Most of the 2017 and 2018 models have the TRUMA waterheaters. Our 2016 came with an Atwood waterheater (TERRIBLE!!!!).
Any movement away from the schwintec slide system is a definite plus. Our kitchen slide has the schwintec system (knock on wood, no problems) but the entire system is kind of lacking in power overall.
We have been happy with our choice of a 38A. The floorplan works well for us. The coach is well built and sturdy. Other than the terrible atwood waterheater, we don't have any real complaints about ours. We ordered ours from Motorhome Specialists in Texas, I don't think "can't order XXX year" would be a problem for them. We were real happy with the dealership.
Good Luck in your search and welcome to the Berkshire Family!