Once you get close to picking brands out, do searches here and include the archives of over 1 year. You can find out about the warts that way. Youtube has a lot of walk-throughs of various campers to get more ideas about what floor plans are available overall.
A key consideration is to remember that even a DRW can be stretched with some of the heavier campers no matter what the salesman says.
Finally, do a good predelivery checklist. Build quality varies a lot even within the same manufacturer since most of the manufacturing processes are by hand.