What are the reasons for choosig operc vs runit?

I'm already familiar with sysv init, so I'm not asking about it.

It's what I'm using now, as far as I know, being whar Devuan
installed on my system long ago.

I gather runit uses djb's process supervision. I don't know
much about it, except that some packages in Devuan use this
model of process supervision, and that distros vary a lot in
where they place key directories in the file system. Otherwise,
it's straightforward.

What does openrc use?

Or better, where can I find documentation outlining the
strategies used by these various init systems?

And are there others I should look into?

-- hendrik