You are right in the size range where room for overnighting, trailerability, build quality and performance all converge... and there is nothing I know of in the 19-21 foot range that does them all well.
The SJ21 scimps on room and was lightly-built; but that also contributes to trailerability and performance.
Here is a site with a huge list of candidates with links to learn more about these boats.
ShortyPen's Sailboat Pocket Cruiser Guide
My main advice is to consider what you really mean by trailerability. A Sanibel, Mariner or SJ21 can probably be towed by almost anything and be launched in 30 minutes or so. They could be practical even for a 3-hour afternoon sail.
A Catalina, Rhodes, Ranger, O'Day or most any other 22 is much more work to launch and retrieve... I'd only want to do it if overnighting and even then it is a pain.
Make sure you really need / want a cabin. If not, your options open to designs that are generally cheaper to buy, easier to trailer and more fun to sail like Lightening, Interlake, Thistle, Buccaneer (a real screamer), Flying Scot, Highlander, etc. But if overnights are part of the picture, you're really roughing it, or tenting on land.
There are also some Trailer Sailor forums you might visit to gain insights from owners. I think many here are more focused on keelboats.