Ethernet to some, but not other

Sounds like you need to use the boost setup, where Sonos creates its own network. You just need at least one device acting as a boost connected to Ethernet.
It works well for me but I found i had to temporarily rename my WiFi SSID whilst I reconnected each device

I have several Sonos products of several different versions (some new, some 4 years old). I am able to hard wire several of the devices back to my router OR I could hardware a few to each other (playbar to another playbar to a one). In both scenarios, there would be several speakers that must rely on Wi-Fi (no way to connect to router or to any other Sonos). I want to maximize efficiency and minimize the strain on my home Wi-Fi system. How should I set this up?
As suggested, wire at least one Sonos unit back to your router. This sets up the SonosNet wireless mesh between the Sonos devices. It offloads the main WiFi and, because it's a mesh, is extensible since each node can connect to the others.

On a point of information, wiring players to each other when in Standard Setup -- i.e. relying solely on the router's WiFi -- does absolutely nothing. The Ethernet ports are dead in that mode.

Sounds like you need to use the boost setup, where Sonos creates its own network. You just need at least one device acting as a boost connected to Ethernet.
It works well for me but I found i had to temporarily rename my WiFi SSID whilst I reconnected each device
Indeed. However it sounds like your problems were only because some Sonos units were stuck in Standard/WiFi (WM:1) mode. As a general rule, a system will automatically switch to SonosNet mode when a single unit is wired. It can however take some minutes for the whole system to flip over. You should then remove the WiFi credentials from the system, to prevent a relapse.

If any unit doggedly remains fixed in Standard/WiFi mode then often power-cycling it will bring it back into line. In the last resort a factory reset on just that device should fix things.

If I understand this you have some Sonos devices that are out of range of the normal Sonos internal networking and you have to have your Sonos system set to use your WiFi router/AP instead?

I'd wire as many Sonos components as possible and then give the Sonos networking another chance to see if it will do the job. You can monitor the internal network matrix to see how that is working. http://your_sonos_ip:1400/support/review

I prefer wiring each component individually to a switch and then back to my router but you can daisy-chain your Sonos devices to some extent, I think it was 5 or 7. I'd look it up here in the Support section if you are going to do very many in a string.

If you really, really have issues with the Sonos mesh working for you then adding a Boost (bridge is a bit old tech) as a link between your Sonos mesh area and the units that are currently out of range. I'd still wire as many as possible.

You might also look at the "group coordinator" posts here if you need to minimize WiFi traffic.

So you have Sonos hooked to router so using Sonosnet. Then some speakers that are close by - but then you say you have some that are too far from other Sonos speakers to connect to them....can you describe more (distance etc.).

Thank you. They all will connect via Wi-Fi, but my house is very easy to wire in most places, but I want to reduce the burdens on my Wi-Fi network. So it sounds like I should hard wire as many back to my switch as possible and then let the others (where I can’t get wire) do their thing via Wi-Fi. Right? Do I need to do something special with the software during setup or will it just figure it all out? I have a LOT of Sonos stuff in a big house - will eventually have about 5 things hard wired and 4 not hard wired. Any additional advice is very welcome!!! Thank you

First step is you need to understand that I don't understand your situation!

You keep saying WiFi but that leaves me completely in the dark, are you talking about using the WiFi from your router or access point (Standard Mode) or are you talking about using the SonosNet WiFi (Boost Mode) that the Sonos boxes support when any device is wired.

See here: https://sonos.custhelp.com/app/answers/detail/a_id/3046?_ga=2.155753211.1371677846.1521778943-806879575.1508786034

If you are using Standard mode and your Router / access point and the WiFi they provide there is one answer.

If you are using the Boost Mode / SonosNet WiFi there is a different answer.

We need to know which way your system is set up.

Having 1 or more units hardwired means none of the Sonos unit will communicate with your home wifi. They will all utilize Sonosnet wifi signal between the wired ones and the wireless ones and the wireless ones to each other as well.

You shouldn't have any troubles. Some routers can have spanning issues with more than one Sonos hardwired. If you have your network slow down after installation that could be the issue (resolution would be some settings in router or only hardwiring one sonos unit) - best just report back here if any issues.

Sorry to jump into this thread, and I hope I am not hijacking it. I had various connectivity issues with my Sonos speakers, so bought a Boost in the hope it would fix the problems. Its sort of mainly OK now but by no means problem free. What I still can't get into my thick head is, as you say,

none of the Sonos unit will communicate with your home wifi. They will all utilize Sonosnet wifi signal between the wired ones and the wireless ones and the wireless ones to each other as well.

then why do I still see DHCP allocations to various Sonos devices (SonosZP, SonosZB) on my router? The Sonos settings shows all my speakers with IP addresses which look like they are generated from my router, but it also shows WM:0 which I believe indicates the Sonsnet.
If anyone could explain, it might help me get my head round this.

They all communicate back to the router to get their ip addresses through unit hooked to the router. They speak with each other but still Daisy chain back to the router through the wired connection.