If you go for a 5000 pound trailer, you need to reserve about 800 pounds of that Highlander payload for trailer tongue weight going onto a hitch. You can't be loading that SUV up to max with people and their stuff.
It is certainly doable. A friend of mine hooks up a Gulfstream Amerilite 21B to his Highlander and hauls it back and forth between NE Oklahoma and Marquette, Michigan every summer. But it is just him and his wife, and a doubt that the two of them add up to more than 250 pounds.
If I were looking to tow with this class of vehicle, I would choose a 16-18 foot molded trailer (Scamp, Casita, Escape) for the smaller frontal area, smoother profile, and better strength to weight compared to anybody's box assembled from laminated panels. But I'm alone, and these feel more confined with more people, though I know couples who travel extensively with 13-footers.
Even with 6000+ pounds of towing capacity (my one-ton van) I would be most likely to go with a molded fiberglass TT if I were to trade motorhome for a towable.
If you want a slide for more interior room, or just to have a slide, be aware that the slide will cost an additional 200 to 500 pounds, compared to getting the same extra space you would get buying a trailer two feet longer. But then, sometimes a slide puts the extra space where it is more useful. One of my two slides does (the bedroom) the other doesn't (makes the living room large enough for dancing, but no more useful to me than leaving the slide in).
