It has a similar folding feature, but not exactly the same. In TaskPaper all structure (which is where the folds happen) is defined by tab indentation. In FoldingText on the other hand lots of different things create structure… for example a heading contains all other non-heading text after it … no mater what the tab indentation is.
Yes, but you will have fewer formatting options. In TaskPaper you have projects, tasks, notes, and tags. That’s it. In FoldingText you have all of markdown. Off course you can open any plain text file in TaskPaper (including Markdown files), but TaskPaper for example won’t highlight bold text as bold text automatically as FoldingText does.
I think you best bet is to download the free 1 week trial here and give TaskPaper 3 a try: