As I've mentioned here before, I did the OW course twice with more than a decade between the two course. The first, imo, was more thorough because of the instructor's desire to impart knowledge that was "barely" covered in the book/videos (this was before e-learning, but the material was much the same as far as I could remember).
Either way, weighting is still something I'm not sure I have right yet as "weight checks" always seem to be done at the beginning of the dive (with a full tank) and I seem to always forget to do an actual weight check when my cylinder is low again (i.e. ~500 psi where it "should" be done to make sure you're properly weighted). I followed the rule of thumb for how much weight to change going from seawater to fresh water and was still able to transfer 4 lbs from me to an underweighted diver on the first dive without having a problem getting down still (so I was "at least" 4 lbs overweights in freshwater following the guidelines for removing weight). I've dropped 4 lbs from my seawater weight since then, but may still be somewhat overweight. I'm sure I could still use some fine tuning on this and plan to keep working on it.
The number one way I'd say both classes (and my AOW) could be improved would be in teaching "how to be a buddy". I'm not talking just sharing air or doing buddy checks, but putting more emphasis on dive planning, how to swim together in different types of situations, communicating with each other, etc. My buddy during my 2nd OW class ended up much closer to the surface than to me or the dive instructor as, with just three of us in the water, I was staying with the instructor who was leading us while my buddy wandered off.... "stay with your buddy" hadn't been covered well enough for him to not realize that he had to stick with those in front of him. That was in wide open water... following your buddy through narrower swim-throughs/crevices etc should include checking on the guy behind you relatively frequently etc but was never covered in any of my classes. I had an insta-buddy that looked at me once on a 45 minute dive that he was in front for, I could have gotten snagged on the wreck and lost him 20 minutes prior and he would have figured it out much later... "how to be a buddy" should be covered in much more detail and should have the importance of it pointed out repeatedly. It does no good to have your buddy be your spare air source if they're not going to be around you when you need it.
The last area I wish were covered/covered more is how to use various propulsion methods. Flutter kicking is fine in some situations, but I taught myself frog kicking so I wouldn't silt up the water when near the bottom (I'm sure I could use improvement on my technique still, but I'm working on it) but many don't have a clue. I went first on the swim-throughs on my LOA because my buddy couldn't get it down and I wasn't going to get any decent views following him while he kicked up the silt..