Welcome to Micro.blog! I just checked your blog and both feed.xml and feed.json have the same posts. It’s possible it hadn’t quite finished updating when you checked it. We include both formats since some apps may prefer JSON Feed, but we also want to include RSS for the most compatibility.
The podcast.xml feed will include any audio posts when subscribed to Micro.blog Premium. We should probably exclude that feed for people who don’t need it. I can look into that.