The experts have put it in the palm of your hand already . Use Trueplay on your phone and it will tone your speakers in each of the rooms. Then you can adjust bass and treble levels to your liking. If you are using an android phone, this may be a problem, but you can ask a friend to use their iPhone to do this procedure

You can find Sonos Professional Installers via https://www.sonos.com/en-us/storelocator

What do you consider to be “the best sound performance from my Sonos equipment”? They could set it up to an “ideal” setting that you think sounds terrible. Trueplay, as already suggested. Maybe try the speakers in a different location. At the end of the day, though, use your ears as the tuning tool. 

Installing wall-mounts and such? Any local audio specialist with good reviews.

They likely could hook everything up and configure the system too.

Adjusting the sound of the Sonos, there you will find nothing better than your own ears. As said use the Sonos tuning tools but don’t hesitate to fiddle the results until it sounds good to you.