Finish on edge of wall join

We would always recommend trim if using ceramic tiles, both at the side of the tiles extending above the half height tiles as well as across the top of the half wall tiles. This will leave a more professional finish. If tiling adjoining walls, i.e. first wall is tiled to ceiling and adjoining wall is only tiles half way up, we would use trim across the top of the half tiled wall and a good quality sanitary silicone in the corner of the walls all the way up to the ceiling. This will allow for movement, grout in corner will tend to crack over time as it is not flexible.

It would also depend what room if its a bathroom grout then silicone if its not then I would just grout the edge

Any exposed edge or corner should have a trim to give a Professional finish to the job