Find the camper you need and go from there?
If you are concerned with payload (a hotly debated topic around here), a popup camper will work on your truck, while you probably won't find a current hardwall significantly lighter than the 650.
Either camper will have limitations on what you can use it for. I think the best approach would be to find out what you are planning to do with the camper, where you will be going for how long, which amenities are important, etc. Then you can (maybe) find out which camper is best for you. And then you can see if and how your truck comes into the picture.
A common saying among TCers is "you can't have too much truck". There is some truth to that, but not everyone can fit a duallie truck into their household plannings. But getting the smallest and lightest compromise of a camper may also turn out to be a costly mistake half way down your first trip.Only you can know what makes you happy.