I will add my opinion:
We also do a lot of "boondocking," but there are different types of boondocking. We are weekenders. We have school-age children and 40 hr/wk M-F jobs. Our "boondocking" is generally 2-5 nights "dry camping" in ORV parks or "primitive" state parks, NF, etc. If the trip is longer than that (rare) we will break it up with a night or two at a premium resort type place in between. There are others on this forum that go weeks or longer without hookups in very isolated areas. Those people would choose a different rig than we would, and make different modifications. Something to keep in mind while reading replies.
This spring we purchased a brand new 23' class C (24'10" actual) with no slides and a corner bed. This is our third RV since 1996 so we knew what we wanted and this floor plan worked best for us. We have been shopping for many years and all the manufacturers made this same floor plan so it was all in the details and the price for us. The smaller, simpler no-slide floor plans also have more towing capacity which is good for us as we tow ~4000-5000 pounds of ATV's often. But everyone's situation is different.
There is very little difference between the E450 and E350 after 2016 based on my research. They have identical engines, transmissions, cooling systems, transmission coolers, brakes, and axle ratios. My understanding is there are subtle differences in the frame thickness and rear axle width however this is more dependent on wheelbase and not E350 vs E450. There are also differences in rear spring pack rate and sway bar rate depending on wheelbase and final GVWR. Take this with a grain of salt as I can not confirm but this is my understanding after much research and discussion with Ford staff. You state you are looking for a rig in the 2014-2015 range and I am not as familiar with that era. I will say the 6 speed transmission (2016 and newer I believe) is amazing and worth considering.
My personal opinion is to select a floor plan you like first, as all manufacturers make all the same floor plans. Floor plan is most important and cannot be changed later. By "floor plan" I'm including inside/outside storage, wheelbase/overhang/tow capacity, etc.
After you selected a floor plan you can look at the different manufacturers options and compare the details (storage, tank size, number of batteries, construction quality, price, etc.) Once you have narrowed to a floor plan they will probably all have the same chassis with same specs so don't sweat that stuff.
All just my opinion