ok, I'm willing to help as much as I can. I think in the tactics section it's mainly going to be just using tactics trainer. Other than that mainly chess mentor courses and articles, which admitedly I wouldn't really have to many suggestions for either.
In the endgame section finishing off the principle of 2 weaknesses video course by Rensch would be a suggestion.
As for the openings it really depends what openings you want to play, but I found the queen's gambit video series by Shankland quite good, and maybe more of the Ruy Lopez course by Shankland to follow on from the intermediate plan. Also the pawn structures 101 course by Rensch is excellent, watching all the basic ones and then the caro slav ones is bound to help, I haven't watched all of them yet and I think there might be another one out on the sheveningen but the ones I have watched have really helped.
Advanced Study Plans
Looking at the Study Plan page, it seems like a ton of people are still waiting for the Advanced Study Plans to finally come out. However, since chess.com is currently dealing with some other matters, I have decided to go ahead and create a page for members to create their own study guide.
Here's how it will work: I will create 5 categories (the same used in the Intermediate Study Guide), and chess.com members can suggest video lectures, articles, chess mentor lessons, and assignments for each category. Please name the category the lesson should be in, and remember that this is for players with OTB ratings of 1800-2000.
#1 Advanced: The Opening!
#2 Advanced: Strategy!
#3 Advanced: Tactics!
#4 Advanced: The Endgame!
#5 Advanced: Bringing It All Together!