Yeah they'll secure the camper fine. No they won't have any appreciable give to them like dedicated camper tie downs with a spring cushioned attachment. That said I'd be more worried about what you're going to attach them to on the truck if you don't have camper mounts on the truck. Don't be that guy with straps cranked down around the bed sides, unless the truck is a beater. You'll likely do body/paint damage.
I tie down scarier loads than a camper with 2" nylon straps. On a camper, I'd be conscientious of any major twisting of the truck frame though like in and out of driveways etc with a hard attachment. Hard to quantify how much twist is seen by the camper mounts and the pressure on them.