Many questions before any worthwhile comments can be made.
What were your former RV's? In other words, what bias do you already have in terms of space and storage requirements, and comfort standards?
How old are you and yours? If over 65 yrs., be sure you can make it up the steps of a demo camper; make it up the big steps to the bed; sit on the pot; take a phantom shower; and go thru all the motions in the head to see if it's for you.
Check out every single storage space in a prospective TC and compare that cubic footage with the amount of stuff you normally carried in a previous RV. Are they close?
How much power do you normally use? The answer dictates whether you need solar, or a generator to get you thru a weeks' boondocking.
How much water are you used to using? Check the size of a prospect's
fresh
grey
black tanks
This is crucial for any kind of extended stay off the beaten path.
If you do not plan any dry camping or boondocking, then it just doesn't matter how big the tanks are.
Do you have ways to stretch the water capacities both fresh and grey?
Is the advertised weight of the prospective TC within, or close to the GVW of your 3 series truck? As said above, you can choose to ignore the letter of the law in this case if it's close. I'm about 600 pounds over the sticker GVW on my Dodge. That arbitrary number got superseded by going to much higher capacity tires and wheels. If yours is a duallie, so much the better as your choices in TC's go up exponentially. Since you have a long bed, you are in the drivers seat. Let your search canvas go out at least 1000 miles.
Report back on what you decide. Inquiring minds need to know.
Good luck and regards, jefe
'01.5 Dodge 2500 4x4, CTD, Qcab, SB, NV5600, 241HD, 4.10's, Dana 70/TruTrac; Dana 80/ TruTrac, Spintec hub conversion, H.D. susp, 315/75R16's on 7.5" and 10" wide steel wheels, Vulcan big line, Warn M15K winch '98 Lance Lite 165s, 8' 6" X-cab, 200w Solar