Jim Lesurf wrote:

A lower amplifier input impedance might also provide lower noise.

No. The source impedance sorts that out regardless.

At some point the coil inductance, etc, may cause a resonance. Probably
well above audio, but might make something like RF pickup more possible in
some circumstances.

It's *mechanical* resonance that's the issue ! A low load resistance can damp
that. The same happens with some well-known microphones btw.

Graham