Any app that can look at synced Markdown files on iOS can be used in tandem with Obsidian on macOS. So, if Bear provides e.g., Dropbox syncing, just point both apps at the same files and you should be good to go.
Drafts is a different story, as it intentionally does not provide file system access for its files—a fact that has long broken my heart. However, it would be trivial to create actions to save Drafts text into the repository you use for your Obsidian notes.
The beauty of 1Writer is that it recognizes almost identical syntax as Obsidian, so you can use both apps in pretty much the same way. I’m not sure if that’s true for Bear or Drafts.
