Unsubscribing from notifications for a specific conversation is the only useful feature here. Muting words/hashtags from showing up in your TL would have been useful. Regarding "online abuse", shared blocklists were much more useful than locking or suspending accounts, that's not going to help at all.

Also I wonder what exactly falls under 'behavior that incites fear about a protected group' and 'repeated and/or or non-consensual slurs, epithets, racist and sexist tropes, or other content that degrades someone'. Will Twitter enforce politically correct tweets? Is NSFW content going to be banned because it offends some people?

I think it's reasonable to ban calls for violence against individuals, but I don't think banning all sorts of hateful content is a good idea and it's not going to help removing it anyway. If people don't want to see certain content, by all means, let them hide it from their feed and notifications.