May I still chime in here?
I actually don't think that a WiiM streamer is the right approach if you want to stick with the SONOS players. First of all, Era100 and Roam 2 are streamers in their own right. They have their limitations, I know, I still own a handful. Adding a streamer to control a streamer does not only make existing SONOS functionality useless (and you have paid for that), I would also expect the sound quality to be less good if the analogue signal from the WiiM has to travel through the SONOS circuitry. That's after you'd have paid, say, for a WiiM Ultra with presumably excellent sound quality.
Was there a problem with connecting the turntable directly to the Era 100 using the Sonos dongle? I mean in terms of available space? If not, I'd start doing that. No double circuitry, less clutter.
To stream amazon music from your Android phone to the SONOS speakers using the original amazon music app, I'd install one of the several apps from Google Playstore which add AirPlay to Android devices. And, of course, as SONOS is all about streaming, add the amazon music account to SONOS (which you probably have done already anyway). The new SONOS app is not the greatest, but it works.
You have a NAS, why not use it to its full potential? First of all, store your personal music library on the NAS. Link SONOS to the library on the NAS and use it with the SONOS app, OR
Install a free DLNA server like Minimserver on the NAS. Control it with one of the many DLNA apps for Android, e.g. Bubble. Select a SONOS device in the DLNA app and avoid the SONOS app that way. Older SONOS players sometimes don't support this, but Era 100 and Roam 2 do. That's what I do when I'm annoyed by the SONOS app with its limited browsing capabilities.
I'm not trying to get you away from the WiiM, not at all, I love the WiiM streamers, but I think they would be wasted as a streaming bridge, while the sound quality is determined by a SONOS player.