When tiling floor, what around the tub panel (plastic), do you trim it? ...
Answers: Tile against the fiberglass tub? Cut the tile leaving in the order of an 1/8" gap and caulk it. When the tub flexes, and it will, if you imbue the gap near grout, the grout will crack. Doesn't matter if hermetically sealed. There are caulks that match the grout color. It is the best instrument to prevent water seep down to the subfloor.
Yes it's the best way to stop sea going under the tub and causing mould.