From what I understand SAC305 if not exposed to corrosive environments has a relatively low (but nonzero) risk of whisker formation. But in practice in a hobby environment it's not going to be a big issue.

Pure tin (or Sn99.3Cu0.7 alloy) is garbage, the silver helps a bunch.

For demanding applications there's apparently some even more performant alloys available today, eg. Innolot [1].

1. https://www.intechopen.com/chapters/55827