IMO, It will look good as is, but on the first landing you could..

Scribe the line of the lower edge of the landing top molding across the end of the descending stairway top molding, then trim the end of that molding.

Likewise trim the lower descending molding to be inline vertically with the bottom stair riser.

Move the vertical molding right, after notching (like you did the 2nd landing) for the bottom stair-nose. Damage to the wallboard will be covered by the inserts.

You already have the second part of the staircase worked out in the picture caption.

Top landing bottom molding, I would just use wood putty to fill the gap.

Nice work. Have fun with it.