Earlier this morning, I used the Phonak PartnerMic at public speaking venue complete with pipe organ, cathedral ceiling, and stone floors.
There was zero observed lag of sound to optical.
As to echo… The PartnerMic actually corrected the natural echo (i.e., reverberation) occurring in that venue.
How? Well, my PartnerMic was clipped onto the gooseneck riser of the lectern mic.
But then on my smartphone’s hearing aid app (Easy Line Remote for KS 10), I was able to adjust the Ambient Balance setting. By sliding the pointer between Surrounding and Mic, I dialed into the desired level of reverb.
The resulting sound was comparable to (read, just as good as) streamed audio from a podcast or YouTube video.