Hanging up Brakes

Ok so for the last 2 years that I have owned my TDI I have nothing but issues with the rear brakes. I drive a 2001 Jetta TDI and in my time of owning it I have changed the rear brakes three times and the front ones once. I have tried multiple things to fix the problems I am having. I have changed both e- brake cables, all the flex hoses and the calipers and I even bought and installed the springs that help depress the e-brake. None of these seem to help and I still have the issue of my rear brakes hanging up. It’s so bad that I am seeing a monumental decrease in fuel efficiency and while driving I can feel the drag they are putting on the car. Please help me fix this.

Rear brakes are pretty simple. If the parking brake cables are not adjusted correctly (easy to check), or if garbage rebuilt calipers are used, you'll have problems.

If they are dragging, you will have hot brakes after driving a short distance. Is that the case? Both sides?

Are the FRONT brakes working properly?

If you detach the cables from the calipers, does it still happen? Does the parking brake lever return to the rest position on its own on each caliper? Are the pads moving freely in their perches? Is there any uneven wear?

If you crack a bleeder loose on the rear, does fluid come out with any pressure and does the wheel get easier to turn?

I'm going to guess Autozone (or similar) calipers???

I have adjusted the parking brake cables to work as they should normally. The calipers I installed were brand new and I have replaced them twice hoping maybe I just got a bad set the first time.
The brakes do in fact get warm after driving and it is bad enough where occasionally you can even smell the pads burning. The passenger side seems to be the worse of the 2 and I think it always has been but the driver side is still bad on its own.
In my opinion I would have to say the front brakes are working as there is wear on the rotors. I don’t think the front brakes have to work as hard as they should however. I often slow the car by engine braking and with how bad the rear brakes are hanging up I assume they do most of the work when coming to a complete stop.
I personally have not tried detaching the cables to see if it helps. When I replaced the brakes last I also installed the Volkswagen manufactured springs that are meant to push the e-brake levers on the calipers back to their home position so I’m hoping they are doing just that.
I will have to put the car up to determine if the pads are wearing unevenly but in the past they have been evenly worn down just much faster than they should be. I will also have to get back to you on the condition of the fluid when leaving the bleeders. What should I be looking for? I know there is no air in the system as the brakes were thoroughly bled.
The few questions I have is could this be a result of a bad brake booster and could it be as simple as doing a complete fluid flush on the vehicle. Also can the rear wheel bearings play a factor in this as I believe I will need to replace these soon?
I appreciate the help just want this headache gone.

The booster failure issue is for some reason usually limited to 2002 MY cars, but that has just been my experience, and it is pretty brutal, as the car will stop on its own when that happens. And it is ALL the brakes, not just the rears.

That is why I suggested cracking the bleeder loose while the brake is "ON", or at least, when you suspect that it is dragging. If there is pressure in there, that squirts out the bleeder, and suddenly the wheel spins freely, then that means you have an issue of something holding hydraulic pressure in the system and not allowing it to release when you let off the brake.