All of this is sound advice.  I do something similar with my live streams.  It took me a while to find my niche, which is retro nostalgia and really obscure games.  People tune in to see what old game I'm streaming, and also to see what game they've never heard of I'm going to pull out next.  And for me, that works! I have built an audience around my live streams that encourages this, and people know exactly what they're going to get when they tune in.

To your point about posting only in English.  I honestly want to see more sub-communities form on Hive.  There was a user back in the Steem days named @pipiczech who would write her posts in both Czech and English.  And I appreciated that, because she was making an effort to bring the Czech community to Steem.  Look at the German and Japanese communities here on Hive.  They exist because someone started it and brought their friends.  And that's exactly what I want to see out of communities here. If I were fluent in other languages, you bet I would be posting in those languages.