Except for the tent campers like QuickSilver, the lightest popups are going to be about 1200-1500 pounds, with GVWR around or over 2000 pounds. I depends on size and type. For example, from 2012 and 2013 Jayco and Rockwood brochures:
Cold-water campers with ice box, no heat or A/C, 10-12 gallon water tank:
8-foot box 1200 empty, 2000 GVWR
10-foot box 1400 empty, 2300 GVWR
12-foot box 1500 empty, 2400 GVWR
A/C will add 100-200 pounds, depending on size installed. This is never in advertised weights for tent-wall campers, because A/C is optional for the type.
Hot-water campers with 2 cu ft fridge, hot water, 15-20 gallon tank:
10-foot box 1700-2000 empty, 2600-3000 GVWR
12-foot box 2000-2500 empty, 3000-2500 GVWR
14-foot box 2400-3000 empty, 3300-4000 GVWR
Again, empty weight does not include weight of optional A/C. Furnace is sometimes still optional, but is not a big addition to weight.
The 500 pound range on the larger boxes is the difference between having a slideout or not having a slideout, which is usually a dinette. Some of these models have an option for a cassette toilet/shower combo, which adds about 600-800 pounds depending on whether that includes waste tanks for the shower. This added empty weight cuts into carrying capacity, there is usually not an increase in GVWR.
Then there are high-wall pups, 12 to 16 feet. The greater height means more cabinet room, allows for a larger refrigerator. These might go over 3000 pounds empty, up to 4500 GVWR at 16 foot.
There is a balancing act, how much room, how many comforts you want. The offering range from not much more than a tent up off the ground, to a fully equipped RV that happens to be covered with tent fabric. If you try to load too much RV comfort into a PUP it gets heavier than a small TT.
When I was looking at PUPs and small TTs, I was surprised to find that 16-17 foot molded shell TTs (e.g. Scamp, Casita) come in around 2200-2500 pounds empty, even when fully equipped with A/C, heat, and bathrooms. This is considerably lighter than a comparably equipped 14-foot high-wall folder.
Of course, TTs this small do not have the room of a pop-up, and with two adults and two children you often have to sacrifice that bathroom to get bunk beds instead, and the adults' bed has to convert to dinette for the day.
