Only weighing in at 276 triangles still - proud of that.
Okay a few hints - I accidentally had one of the mesh analysis fields set at 0 rather than 0.01 or 1 etc - which highlighted non-problems. Also there’s something that is supposed to Cleanup non-planar faces under the cleanup menu.
My method of creating the crown differed a little. Not sure if it’s any better or worse but here’s the notes.
I did a loop cut and placed it exactly at the same z as the inset edge for the crown
Sub divided just the top edge to give me points, then went around deleting just the outside faces. Then selected three verts that made up each point and filled in the face.
On the other side I Alt-Selected edges between the point and inner loop and deleted edges and faces. Then selected 3 verts at a time and filled them in one by one. I started going left to right, but then found doing the two triangles on each side then the inside big triangle was easier.
I did end up having to delete verts floating in the air because they were not used by the points of the crown anymore - but that wasn’t too bad.
Anyway because I didn’t subdivide the faces I think I ended up with less clean-up? Not sure. It certainly did seem like a bit of a chore anyway. Also I have now have an even greater respect for how much planning 3D Modeling Artists have to do - feels like it is using similar muscles to programming. Interesting puzzles to solve 
