Trailer: "The Trailer", 2nd Gen 21' & a 2017 Tundra CrewMax in Blazing Blue Pearl
3 months ago I got to flop on a u-shaped dinette in a 21 footer, as I was very interested in seeing what they were like. As you can see from the photos in the thread (link below), there was plenty of room for me (and I'm not exactly tiny) and my size 11's. I'm 5'10"
Trailer: Escape#4, 2019 Escape21 DejaView pulled by 2014 Ram Hemi/8sp
I'm not sure but I have not seen a flush mount table in a 21 and only in a 19 with raised floor. You may have to raise that entire area to get the flush mount as the fresh tank is right underneath that area.
What you get by achieving your goals is not as important as what you become by achieving your goals....
Since the socket is much deeper than the thickness of the floor, there must be space under the floor for clearance. In some models the freshwater tank may extend far enough back to be in the way, and even if there is no tank I still wouldn't want the socket sticking out through the fiberglass shell (although I recall someone doing that as reported in FiberglassRV); the raised floor provides the needed space within the trailer shell.