Ask HN: What's your best Hackpad replacement?

Hackpad, while great in it's simplicity and speed is lacking many features (such as grouping of documents) and since Dropbox bought it, it seems an EOL product.

I've been trying Notion.so, and although it has solid features, it's not as snappy (at all) and has quite a few quirks there that are quite annoying: you really notice that a page needs to load, it doesn't remember in the folder tree what was collapsed or expanded on a refresh or when pressing back.. and several other settings like "full-width" etc are on a per node level, instead of global, and so on.

So my question is: what collaborative writing software do you use, that has some kind of collection/folder features to group documents, and that is blazing fast.