Electrical panel emergency disconnect, ground rods and sound quality

I finally pulled the trigger on upgrading my house old electrical panel (load center) setup that wasn’t properly grounded.

I went with the Square D QO series panel, whole house surge protection and 2x8' ground rods and 4ga solid copper ground cable per NEC code. My electrician drove ground rods at a 7' distance between them per code. I learned too late that there is a recommendation for optimal distance between ground rods to be about 2x the length of the rods. Oh well...

Even so, I could clearly hear improvement in my system and it was not subjective. I no longer hear a transformer-like buzzing noise coming from my speakers that would increase with volume. Instead I hear a much softer noise similar to an AM radio being tuned. I have to be right next to tweeter and volume up pretty high to hear it. I’m sure that noise was always there but masked our before the upgrade.

City inspector, however, faulted new panel install for the lack of an outside emergency disconnect between it and the meter per NEC 230.85. My electrician thinks it’s completely unnecessary and that requirement will be done away with in the next NEC revision, but I digress.

Is there an opinion about which brand/type of emergency disconnect has the least negative effect on the quality of power coming into the house?

How much my ground effectiveness has been reduced by having distance between ground rods be less than 2x their length?

All in all, I highly recommend this type of upgrade for older electrical systems!