Write content locally and then post to both to reach more audience. After a few posts, you'll see which one benefits you most.

Well it depends with your specific goals like do you intend to monetise the content or it’s a labour of love? If monetisation is in your plans I recommend having both, as that will ensure the greater number of eyeballs from both parts of the world (ie the fiat world and the btc world) Hope that helps.

This is one of the cool things about nostr's interoperability. If you post a long form note it will appear in all the places you mentioned with no extra work on your part. You can see my articles on yakkihonne, habla, and npub.pro. I wrote them once and they are available to any client that supports long form notes.

npub.pro might be worth a shot if it publishes RSS feeds