"Jeff" wrote
| Do they have different meanings?

Yes! One is wide for wide water (give way) and one is narrow for narrow channels (shall not impede).


| Can both be in affect?

Yes. If you do the *shall not impede* you do it by giving way.


|Which would take priority? What does this really mean in practice?

Shall not impede takes priority because it's narrow for narrow channels.
In practice it means the same thing. It means give way.

Cheers,
Ellen