I will give this a try on Sunday.You haven't said which motor
I have mine attached to the gear outer just infront of the cable port on the downtube. This means the lights are obscured by my bars. I find the lights annoyingly bright (especially at night) but if I want to see mode or battery/warning light I just have to move my head slightly to see below the bar.
I find the New Orbea's EW100 location really ugly and somehow makes it look massive in the pics/vids.
With the Garmin 530,830
Garmin's wireless speed and cadence sensors will override the speed/cadence data transmitted by the motor if fitted to your bike.
You will require them if you're running a derestricted set-up otherwise your garmin will log your rides as half the true distances/speeds