For example, what's a "sub stream"? What's an "ext stream"?

The former I could find hinted in one part of the README, but no clue what an "ext stream" is or if I should have or want to have one.

What's an onvif_base_url? Would be nice to get some example for some cameras, or some way to check whether I picked the right one, or an explanation what feature is being enabled by that.

What does [ ] record do? Should I enable it? If I don't I seem to get this issue in the live view:

aborting due to Must have sub stream set to record; see #119 and #120

If I need to record anything I want to see live, what's the point of having a lower-resolution sub-stream at all?

I understand some things might simply be not implemented yet, but it would be nice if the UI could explain today's purpose and effect of settings, instead of requiring issue tracker research (it's totally OK to write in the UI "you need to currently enable XYZ because otherwise something isn't implemented yet).