I am opening this as both a feature request, and as documentation, because it's been now at least twice that I saw this being asked by newcomers on Gitter.
The current way to be importing D7 views post-installation, is to be using the contrib module https://github.com/backdrop-contrib/default_views_config to convert exported D7 views into config, and then to import those into Backdrop via /admin/config/development/configuration/single/import.
With all the expected D7 sites upgrading to Backdrop over the next couple of years, we should make it easier to do that in core (we could remove that in Backdrop 2.0).
At the very least, we should make sure that the process of using the contrib module is documented in a place where people would expect to find it. Perhaps even consider a help message in Views, pointing to the contrib solution + online documentation.
Recent comments
You can use Rules or the Node Notify module for comments. When a new account is created, I believe there are Rules to send.
Email notifications
There's a few way to accomplish it, but it really depends on your full requirements. I'm working on a contact management module but it won't be released for a few months. There...
Pairing fields
I'm fairly sure that some people have done this successfully in Backdrop. Please can you list the modules you are using; that should help us get the right people to join this conversation.
How to render facet blocks?