I'm an RWA member and entered a metric cr*p-ton of contests years ago before being published (and still like to enter the contests for published books). The Golden Heart is just a score--no feedback--but chapter contests almost always have feedback in the form of score sheets with the criteria the judges use to judge by. The quality varies--some are excellent, some not so; it comes down to (a) how well the score sheet is constructed and (b) the quality of the judges. Most contests will post their score sheet so you can have a look and decide if your entry is likely to get good feedback. But there's no way to know ahead of time what your judges will be like. I had amazingly helpful judges who gave excellent feedback (it was a contest judge who helped me realize that what I was writing was YA fiction). I also had judges whose feedback was worse than useless--it was ignorant and flat-out wrong, like having already correct grammar and usage "corrected" or having my history "corrected"--I was once told that women didn't go to college in the 1920s and that I should do better research (*facepalm*) And just once, I had a judge who utterly savaged my entry, giving all aspects the lowest possible scores...except I'd sold that manuscript about two weeks before getting that contest's result, and just laughed. But she evidently had an axe to grind.
So yeah, they can be very useful...or not. It's a gamble. Maybe enter one or two of the better ones (again, look at their score sheets before deciding which to enter) and see what you think. Also, there are a few specialty chapters (Regency, YA, historical, paranormal, inspirational, romantic suspense, LGBTQ) so if you're writing in one of those sub-genres, have a look at their contests.
Good luck!