As many have already said, payload, payload, payload.
Payload is the tow vehicle's capacity to carry everything and everybody you put in, or on it. Look for a tire / loading sticker on the drivers door post. It will show a cargo carrying capacity (AKA payload). That carrying capacity is used up by the weight of aftermarket accessories, people, pets, weight distribution hitch (about 100 lbs), tongue weight from a trailer, and all the "extra stuff", packed into the vehicle.
If you know the total weight of your people, pets, weight distributing hitch, and "stuff", subtract that from the vehicle's payload. The remainder is your carrying capacity that is available for trailer tongue weight. Divide that number by .13, to get a ballpark figure for a loaded trailer weight that will keep you at or near your ratings.
4WD might be nice if you get stuck in the mud, but, it is not a must for towing. If your towing will be on improved roadways, there is no need for 4WD, and rear wheel drive is fine. 4WD also adds weight to the vehicle, which reduces it's available payload.