- For 1, partly yes and partly no.

When you broadcast something, you're sending a copy of the post to relays you're connected to (ensuring it reaches relays the original author is not connected to => widening a posts availability on different relays).

Boost also does that, except all your followers can see your boosted post => it also widens reach of a post, but among users too.

- For 2, they just show different kinds of posts - one is notes & the other is videos/images, specifically NIP-94 kind