@theaudioamp that is all good and correct, and we should minimise ground loops, and using one outlet or circuit is a help.
But every one in town is rattling their noise onto the power line, and those fields are going into other circuits in our house, say to another parallel circuit in our house… and out of our house into the next house… etc.
And I doubt that a 12ga romex brand wire bundle is much different from some off brand of 12ga copper wire.
Having the LEDs on different circuits makes their effect at least need to travel further to get to the circuit that our gear is on. Ideally that is on a different phase of 120v, so it needs to effectively go to the pole where the transformer is at in order to loop any fields back. (It is that way if we ignore coupling between the two phases.)
So I am more inclined to trust the electrician (aka “a sparkie” in Australia), and then put the investment of power conditioning into the gear which is generally designed better to mitigate noise entering in.
But a dedicated circuit and grippy outlets are never a bad thing… just it is doubtful that some fancy copper will change anything.