Whatever you use, throw a submersible pump on top of the cover to collect any rain water you can use for watering your plants. Up North, my pool was about 21 wide and I put a pole across it from which I suspended the pump so the pump wouldn't get clogged with leaves while I was pumping water off the cover. Water is very heavy and even using inner tubes or beach balls didn't prevent the accumulation of water on the cover. Neighbors of mine gave up and just kept their pool uncovered and the filter running on low speed during the winter. They could shock as necessary and the pump , always on, didn't risk freezing and blowing out piping.

We don't cover ours.