Play everything through 2 Sonos Ones?

For your first question, the answer is no. Each device operates as a separate Alexa device, You can't have them operate as if they were one, no matter how they are setup in Sonos.

For your second question, if you want them to operate as left and right channels in stereo, then you want to pair them together. If you want them operate as searate mono speakers, then you want to group them together, as two separate zones. I imagine you want them as a stereo pair, as that's the typical setup, but I'm not sure if that's you intention based on how you've chosen the speaker location. Typically, stereo speakers are setup along one wall, pointing in the direction of the most common listening area. I don't know if that fits your setup.

Yes setup Alexa on both as they will chose the one you are closest to in getting voice commands.

If the both face the living room I would probably setup as a permanent stereo pair (one acting as right and the other as left). Otherwise if you want full stereo from each then you would want to group them.

Thanks for the replies and advice. I ended up setting up both Sonos Ones against the lining wall of the living room and paired them. Alexa responds from one speaker or the other depending on which was closer to my voice. Nice! And whether I ask it to play NPR or a song from Amazon Music, the sound comes from both speakers. Exactly what I was looking for. The sound quality is amazing!

Thanks again.

Alexa responds from one speaker or the other depending on which was closer to my voice. Nice! And whether I ask it to play NPR or a song from Amazon Music, the sound comes from both speakers.
Question for anyone that has tried this: does the above work in this way regardless of whether the two One units are stereo paired or grouped as two independent speakers?

That shouldn’t effect anything. Echos always all wake up but the one that gets selected as best is always the one to respond. It works that way if you have multiple dots in same room. It’s controlled by amazon server.

Alexa responds from one speaker or the other depending on which was closer to my voice. Nice! And whether I ask it to play NPR or a song from Amazon Music, the sound comes from both speakers.
Question for anyone that has tried this: does the above work in this way regardless of whether the two One units are stereo paired or grouped as two independent speakers?
Yes, it works this way if grouped, stereo paired or even if you have them as rear surrounds for home theater.