If you don't subscribe to any feeds, Bluesky is also a place where what you say will only be seen by people who follow you and people who follow those who repos

If you don't subscribe to any feeds, Bluesky is also a place where what you say will only be seen by people who follow you and people who follow those who repost your posts. Whether or not either of them is a shouting match depends a lot on your choice of who to follow. This is not to say there aren't significant differences, many generated by the federation choices Mastodon (and Bluesky) have made, as you also noted.