So I recently adjusted the float actually because I felt like the water line was maybe 1" too low (it was certainly below the half-way point of the waterline tile). There's a butterfly screw that you loosen which allows me to adjust the float. It is held in place by these "gears" or "teeth" so you can adjust it in fixed increments. I went 1 increment up (which would allow the water to fill more). It has been filling for about 3-4 days now. However, it's at the point where barely any water is coming out (I have to put my ear right next to it to hear the valve running). I assume it'll shut off at some point, since filling at that rate must be very slow. I am not concerned the water will go high enough to drain out, but I am concerned that any waves or splashing would cause water to go through the overflow drain. I just don't want to lose a significant amount of water when we start using the pool more.
Honestly I was hoping the overflow drain was inside of the autofill bucket, because the water is more "stable" in there and protected from the splashing.