I'm glad to hear your large trailer experience went well. I have an identical WK2 down to the year. I'd be a bit intimidated to pull a 29', but I find my 19' to be a great experience. That 20' Jay Feather will be an easier pull for sure.
Since you seem to be trying trailers out and looking for ideas and input.
If you get the chance, see if you can try out a small tandem axle travel trailer. The tandem axle tracks like a dream, and you don't have to worry so much about overloading the trailer with gear and supplies. I have a 5800# gross trailer weight and about 2500# cargo capacity. I don't ever load it that much, but I like not worrying about overloading or even stressing the trailer. We like to get out a ways and often find ourselves without hookups, so I can fill up the water tank along the way and not have to worry about being overweight. I'm usually in the 3800#-4500# range and have a weight distributing and sway control hitch. Tandem axle also gets you twice the braking power. I also like the 19' because I can usually fit in a double space in a parking lot. It's also short enough to get into just about any camp ground.
Mine is also 7' wide which makes driving everywhere a lot easier, especially mountain roads, and also keeps the frontal area down. Though, I will admit that 7' loses a fair bit of interior space, and I don't have a slide out either. For the two of us, we make it work just fine. I'd consider a slide out, but not having one also means it never leaks and never breaks.
Damn, now I want to hit the road.