I'd love to hear your experiences with toy haulers.
2010 Forest River Shockwave 21' toyhauler here (MX-T21FS). Bought brand new. It was the last one on the lot, great price so we took it.
Specs:
3500lb axles, so 7600 or something GVWR.
53g fresh, 40g gray, 40 black.
35g fuel tank, no gen.
Non-ducted heat and A/C.
Full fresh, 2 propane tanks, 1 battery, mini grill and leveling wood in the front pass-through. All our bedding, pots/pans, misc, no toy gas, weight is 5180 on the axles and 1000 on the tongue, so 6180 trailer weight.
Has a front bed that lies East/West. Two fold up 6' couches (one each side) that make into single beds for my two kids. Cabinets line each side of the trailer all the way to the ramp so no drop down beds, but more storage.
You can get a similar sized trailer with 5k axles instead of the 3.5k, but they also weigh more because of the larger frame.
If I had to do it again I'd get a 24-27' and a North/South bed in the front. Other than that our layout is near perfect for the 4 of us with the kids at 7 and 5yrs. For full timing there isn't enough closet space (in my trailer).
I lived in mine during the week for 2yrs in Crescent Valley NV while I was working over there. Insulation sucks... But mine is also an exposed belly. I did add stick on tank heaters (UltraHeat), traced and wrapped the one exposed water line, then skirted the trailer with osb backed with 1" foam insulation. $100mo power bill in the summer or winter. The 13.5k can easily keep up in 100+, and the propane heater was able to make a comfortable trailer in -20 by itself without the skirting.
For everyone knocking Forest River quality, it has been a great trailer. 8yrs later with a fair amount of constant usage, we've broken a plastic piece on the drawer slide and had a piece of interior molding come loose.
My trailer rides great loaded or empty. I had a tv remote on top of a mini pantry (about 8"wide) right above the axles. It rode there for 300mi without my bikes in the trailer. The only time anything has shifted around in the cabinets is after emergency braking.
This will be critical for you.
Think about bike storage vs kid sleeping space vs kitchen table location. In my trailer they are all the same spot; kids' beds need to be turned into couches and the tables set in the floor for meals. 'Toys' have to be out of the way for any of this you happen. Ceiling bunks would be a benefit since you could just raise them still covered in bedding for the day.