Hi, Xavi - thanks for getting back to me. I've just added you as a writer, so feel free to submit any stories you feel would be suitable for the publication. Anything about Catalan language, history and culture would be really interesting to readers elsewhere who tend to know very little about the linguistic diversity of Iberia beyond Spanish, Portuguese, and maybe Basque.
Your Cuban travel piece would also be a good fit. If you like, you can go into the editing interface and should see the option to submit it to Iberospherical, and I would then publish it. The only thing is that Medium retains the original publication date, even if a piece is 're-published', so it wouldn't appear on the home page or be included at the top of the feed. But it may still attract new reads from people following the publication, via the mysteries of the distribution algorithm, and I will probably in the future publish features listing all the pieces about individual countries or geographical regions, so it would be included there.
Entirely up to you. Certainly for any new stories, I think you would benefit from posting them via the pub, as we have nearly 100 followers with an interest in the subject area, currently growing by about 50 per month, and as part of the Boost pilot programme, are now drawing a bigger readership.
Welcome aboard!