Using NDI and connecting to an iPhone over USB, I found the latecy to be pretty low, but still there.
Interestingly on a zoom call a few weeks ago I ended up on a call twice, once from my iPhone, and once from the mac. I had a headphone from each in one ear. Sometimes the iPhone would be ahead by 0.5 or 1 second. But then within a minute the Mac would be ahead. So zoom is streaching out the audio to adapt to network latecy, I guess.
