The rear discs themselves are meant to be self adjusting, so leaving only the cables.
However I have often found that people have over adjusted the cables and so prevented the disc calipers doing their self adjusting.
If you safely block the car from rolling, then with handbrake right off, the handbrake levers at the calipers should be totally back against their stops.
It may be easier with the wheels off.
Assuming the handbrake cables are not sticking at all then with handbrake cables backed right off, if I have a vehicle with a problem or after fitting new rear brake pads I would expect the handbrake levers at the caliper to be fully off against their stops, then I would pump the foot brake several times and the self adjusting mechanism in the calipers should operate bringing the brake pedal up to normal, I would then check that those levers are still against their stops and that there is no brake drag. I would then work the handbrake on and off several times and recheck no brake drag, then if necessary adjust cables for a good handbrake and recheck no brake drag. Finally I would give it a good road test and recheck wheels are not dragging and that the handbrake holds well on a hill.
If cables are fully backed off and loose but the levers are not back against their stops then time for a new brake caliper.