[CentOS] C 7, docker, and storage

I may have missed some overnight replies to my question from yesterday - if so, sorry.

From my googling, it looks like I should change from the loopback device

to overlayFS (with overlay2). What I haven't found is, first and foremost, more clarity on configuring storage.

It *appears* that the loopback storage is just a directory under /var/lib/docker (yet I see a reference in someone's blog to ~docker - *is* /var/lib/docker intended as ~docker?

Can I make a docker directory elsewhere, on another filesystem that has a lot of space, and configure docker to use that, or do I need to symlink from /var/lib/docker to the new place? And should I move all the old stuff under /var/lib/docker to the new location (of course have shut down docker)?

mark