4k-7k is a broad range for an SUV, since most of them these days are at the low end of that, or even less than 4k. By the way, are those numbers the loaded weight for what you want to tow? It's pointless to talk about dry or unladen weight - always use the trailer GVWR unless you have an actual scaled weight when loaded for travel.
As a rule of thumb, you can tow a trailer whose GVWR is 80-90% of the max tow rating for the SUV. That leaves enough tow vehicle capacity to cover the weight of passengers, gear and the hitch in addition to the trailer. Yes, you have to account for such things. At 80%-90% you probably won't be thrilled with the performance and handling, but your SUV will get the job done.
The Toureg probably has the largest tow rating in this group, about 7700 lbs for most configurations. The Pathfinder is around 6000. A 7700 lb tow rating would typically allow you to pull a trailer with a GVWR of 6500 lbs. The 6000 lb Pathfinder could tow about 5400. Both those are rough estimates - would need more specific data on what you will have loaded in the SUV, and also the SUV cargo capacity. Cargo Capacity is important becasue it has to carry the tongue weight as well as pull the trailer, and RV trailer tongue weight is 10-12% of the loaded trailer weight. You are talking 400-800 lbs of "cargo" in the SUV just for the trailer tongue (hitch) weight alone.
