I won't even touch the truck debate other than to say that more within limits you are the less stressful the driving will be if you are planning some long distance traveling.
The trailer is the thing. You will adapt to reversing the 5er. It comes down to what do you want to do? Are you a FHU camper or do you want to do some dry camping? Long term traveling opens up all kinds of events to go to, often dry camping only on site. We do bluegrass festivals whenever we can find them. These are usually 3 night events. Planning Alaska? The very best parks are the SPs & PPs. No on site services. Teklaneeka CG deep inside of Denali NP is dry camping 3 night minimum.
For dry camping freshwater & battery capacity is king. A trailer with a 60gal tank does not cut it. It may be fine for a 2 nighter but that is about it. The larger the battery capacity, the better, especially with at least a 1kw inverter to cut down on time needed to run the genny.
Oh yes, size does matter. Once you go over about 35'LOA your CG options, particularly SP & NP sites, begin to drop dramatically. Big is nice but having to use a private CG miles outside of a NP like Yellowstone is no fun.
Do the research before signing any papers. Don't let the fluffy stuff sway your decision too much.