PaperUI is pretty much just a an OH 2 thing. You will never see Things, nor can you create Things for a 1.9 binding. And I’m not entirely certain you will ever see traditional 1.9 binding Items in PaperUI either. I honestly don’t use it for anything except installing bindings and finding Channel IDs and I’ll probably switch to Habmin for even that.
I think you can create a UI in Habmin (i.e. a Dashboard) but I don’t know if it supports traditional sitemap files directly.
Yes, OH 2 can still use sitemaps. The Classic UI and Basic UI both use the same old 1.x sitemap files and syntax. Habpanel lets you create the UI in your browser (kind of Drag and Drop with some more config). There is also yet another UI that you can install that I know nothing about at this time.
PaperUI is meant to strictly be an administration UI for OH 2 stuff only.
Habmin is capable of being pretty much everything, though I would categorize it as the admin/power users UI. There isn’t much you can’t do through Habmin though.Basic UI and Classic UI are the user interfaces we are used to. Basic lacks some features (e.g. visibility doesn’t seem to work for me) but looks better than ClassicUI which is just a refreshed version of the OH 1.x sitemap. Happanel is great for remote control type interfaces that look something like the Windows 10 start menu (squares and rectangles everywhere).