I use a chaulk line to lay out tile…sorry, I couldn’t resist the temptation.
Most plumbers are not expert tilers, but we have to do tilework on occasion. My experience is limited to building shower and tub surrounds, and the occasional kitchen sink counter. The way I was taught, you grout the seem at wall and floor (or countertop), then caulk the grouted joint. Sometimes these joints are made with quarter cove or quarter round tiles. If you want an expert’s opinion, ask a tile man.