Hi Martin, congrats on your upcoming wedding!

re: when to trim - that would likely depend on what particular piece you are planning on trimming.

Usually you woudl want to use trimming fairly early in the process, but you usually do trimming when you have modeled larger extended pieces to then remove some material from the single large piece to make the final boundaries. When you model in a kind of patchwork way where you actually have constructed individual surfaces that go around different contours and holes then usually that is something that handles features separately from doing trimming.

Usually though you will get a higher quality result buildling a smaller number of larger surface pieces and then trimming those to produce some of the edges in the final result rather than doing a patchwork type process. The patchwork process will make for a complex topology of a lot of interior edges in the final result and you will likely have a lot of pieces that come to shallow angles to one another - either of these things tends to make filleting difficult.

- Michael