Filling gap between Schluter transition strip and drywall

Question

I did a noob mistake in my first major DIY project of bathroom remodeling When I installed the cement backer board I left some gap between the cement board and the drywall. On top of that when I installed the tiles I did not go all the way to cover the transition between cement board and the drywall. Now I have this gap with the Schluter transition strip on the bottom, membrane coated cement board on the back and the drywall on the top. Please see the attached picture. Also note the drywall and cement board are not levelled.

The question is how do I fill this gap? Some options that come to my mind are:

1. Fill it will cement, coat with drywall compound and paper tape and topcoat with drywall compound
2. Fill it with narrow and skinny(1/4 inch thick?) drywall strips, coat with drywall compound and paper tape and topcoat with drywall compound
3. Fill it with narrow and skinny(1/4 inch thick?) plywood strips, coat with drywall compound and paper tape and topcoat with drywall compound
4. Fill it with Hot mud(I have 90 minutes USG), coat with drywall compound and paper tape and topcoat with drywall compound
5. Fill it with foam backer rod, coat with drywall compound and paper tape and topcoat with drywall compound
6. Fill it with foam backer rod and caulk.

There could be other options I am not aware of. I am really confused as what I should do.

Please help!!

Thanks

Answer 1

I just did something similar to your option 3. I used setting compound (Durabond 90) to fill the gap and smooth out it as best as a could.

After I got it pretty level I used a layer of paper tape to create a smooth surface, and finished with a small amount of premixed finishing compound then texture in my case.

You can use the Schluter as kind of screed surface after you cover with blue tape. I changed it between each layer to keep the build up of compound minimal.

Since drywall near water is always susceptible I did 2 coats of primer Zins BIN 123

Then 2 coats of a satin

I'll caulk the transition with a thin bead of clear silicone once I finish the floor. If you look closely you can see the wall bends in behind to the Schluter because its not flat but its not as noticeable from far away when finished.