ActivityPub is a common language that allows describing "actors", "activities" and "objects" -- and as such, can describe any kind of social platform, from blog, to forum, to social media site, be it for photo sharing, video sharing, or something -- in your words -- Twitter-like. Not everything that uses ActivityPub will be 100% identical in user-facing functionality and UX, but most platforms have a concept of subscribing to other users, receiving new posts, and replying or re-sharing posts, which is where the interoperability comes to shine.

If your blog uses ActivityPub, it is still a blog. People could just subscribe to it to receive your posts in their home feed, reply to them, or re-share them in a way your blog could process (or choose not to).