We had similar requirements and we live in the mountains. I don't want to be stuck on a concreate pad looking into the next trailer either and so you are right shorter is better for nature, longer is better for an RV parking lot with all the amenities. And 28 feet or shorter is a sweet spot for places like National Forest campgrounds etc.
The shortest you can get will be in the 5K dry weight range and 25 feetish. For that, you will likely need to have either a Murphy bed approach or a sideways RV queen with the full size bunks in back (teenagers). Remember, trailers are either 7 feet wide or 8 feet wide. Go 8 foot is my recommendation. More room. Have good tow mirrors. A catalina 221DBS is an example. Dry Hitch weight will run 500 to 600 lbs. Here is a sample vid on one. https://www.youtube.com/watch?v=8tTvKx8lV1M
The advantage of this approach is you get REAL "full" bunk beds AND a place to sit other than the dinette. The disadvantage is that you have little privacy for the front bedroom. This type will run 5K to maybe 5300 lbs and 25 - 27 feetish.
The other approach is to have a separate bedroom with doors AND full bunks. Here is what we ended up with an Aspen Trail 2340BHS or BHSWE (western edition). Here is a vid on them a couple years old. They have added some bells and whistles since like power stabilizers and hitch, fireplace etc. https://www.youtube.com/watch?v=R3sXOlpxv-s For the permanent bed AND privacy, you gotta add at least two feet to the unit. Ours is 27 feet four inches and 5500 lbs dry. These floorplans run 27 to 30 feet generally. Our Dry Hitch weight is 614 lbs. Add 200 for bigger tanks and two batts. You give up the sofa sitting.
So, based upon what you indicated these types of floorplans would be my recommendation. There are quite a few of each type with variations from different manufacturers. I's steer clear of the ones that have the small 29 to 32 inch bunks...unless you have small kids and intend to go bigger later... And watch for the small dinettes if you don't go slideout as they will realistically only hold two people of any size. The seven foot wide units usually have these.
And, as you may already know, your gray tanks are the weakness of any system. Our little one had a 28 gallon gray tank and it was good for three days two people and maybe three showers total not each person.
We got ours for 23,600 AND, used trailers are very valuable now days. You will find yours is worth a few thousand more than just two years ago, so either sell yourself or find a dealer who will give you what it is worth. WE had one dealer offer 8K and another 11K so keep that in mind as you deal and negotiate in 2021.