OP, in this market, I'd say the ONE you find, that checks most of the boxes on your wish list, and not abhorrently overpriced, regardless of brand, is the one to get.
ALL RV's new or used, unless they are used and come from someone who is OCD about fixing every little thing WILL need some work.
Components are fairly standard between mfgs (fridge, AC, water systems, etc). I'd call it luck of the draw.
On our 3rd "RV" now and the first 2 were what I'd consider quite reliable with only a few issues (they were truck campers) and the newest one needs a couple things, but at 4 years old and basically never used, the minor issues thus far are either with the mechanical components (same or similar across brands) or simply age related (needs some caulking, new batteries, etc).
On CCC and durability. I'll say, in general, the units with larger CCC are built on a better chassis.
You're looking at trailers with about a 7-9k gvw I'd imagine. Maybe 10klbs on the big end.
I wouldn't even consider (well, in the Covid camper computer chip shortage market, I might....) anything that's 30' long sitting on 14" wheels. Means you'll have 3500lb axles and corresponding suspension, which WILL be running at a high % or max rating. I have a 32' long 7klb gvw enclosed snomachine trailer sitting on 3500lb axles and 14s. Basically an empty travel trailer. It tows great, handles great, 16 years old, no real issues. BUT, it's about 3500lbs empty and I'm never putting more than about 3klbs of cargo in it, usually less. And when I have 5 machines in it, it feels "full."
Any of the trailers with 15" wheels will have 5klb axles and presumably heavier frame with more headroom for weight carrying capability. Which adds up fast. 3 kids, bikes, wife buys a bunch of outdoor "accessories", you toss some 6V batteries up front, cram a few pieces of firewood in the storage, water tank full. Got enough food and drinks to live for 2 weeks for a 5 day trip, etc...
Good luck in your search, just my 2c to help your decision or hopefully not further the conundrum!