I think the silicone added makes it an adhesive caulk. The tube I had on hand is the stuff that turns clear after it dries. I had done just one side and stopped for the day. When I came back and looked I at first thought the caulk had shrunk as the gaps were back. When the caulk was still white the gap disappeared, white (primed) crown molding and white ceiling. I will open another tube of the stuff that stays white. I think for inside use the straight (simple) acrylic latex is sufficient.

The only type of cabinet that won't show lines/gaps are traditional partial overlay doors. Inset doors will show a space between the door and the frame, but frameless doors will also have small spaces between the doors and the moldings, and also between the doors themselves. There's no way to avoid this because you need clearance for the doors to open. AND the spaces will not be even either. You just need to accept it and forget it!

"Well, it's not really crown, but more like a flat board to fill the gap, and a strip of cove molding along the top to make up for the uneven ceilings." This statement heads me in a different direction. There's a joint between the two cabinets now. If you are basically putting in flat fill pieces (as you would do in a modern kitchen) I would put in two pieces of wood, with the joint lined up with the cabinets, and paint each the color of the cabinet below. Since this is usually done in a modern kitchen that's the example I found and you can see below they extended the color of the cabinet below up to the ceiling. I realize you don't have a modern kitchen -- but you are proposing a modern style fill strip for the gap so here ya go:

I'm surprised the installer didn't address that during installation. I would have used an extra piece of trim, in the same color and flat, and installed it behind the crown molding. Thus, there would be a flat white area where the gap is. Yes, it would still create a visible line, but much less visible than a shadow or gap. Since the crown is already installed, caulk.