“Which apps” depends on the format of your documents – markdown, plain, rich, PDF, etc. Let’s take markdown for example. I have been using Notes Writer+, Ulysses, and Textastic with markdown. Some other apps are a bit cranky with document provider – 1Writer refuses to recognize most files in DTTG that are flagged as “markdown”, but will take plain text files containing mark up – which is odd since 1Writer is a markdown editor.
Mellel and Word on iOS are the same way with rich text – they don’t recognize RTF/RTFD files in DTTG in the document picker as being editable by them. But Word is fine with Word files, as is Pages. I haven’t found an RTF editor on iOS that works with DTTG’s files in document picker. Maybe that’s a DTTG fault?
BTW, I find working with Editorial is a lot easier nowthat it supports split screen. It doesn’t use document picker, but with split screen the round-tripping process is fast.