I regret getting the slide toppers. They do nothing but flap in the wind. I know they can be a plus for keeping debris off the slide tops, but the flapping noise is maddening. And to think I paid extra for them.

Our last trailer did not have them and I don't think our next one will either.
We do not have the Trail-Air hitch or the Mor-Ryde and don't miss them either.
As for factory tires, just make sure they are at 110psi when you take delivery (our dealer had ours at 80psi - too low for H load range tires and this much weight)