Best sub for Beam Gen 2, 600 SQ FT apartment

Sadly the mini wasn't being made when I bought my Sub, trading now would be expensive for what seems to me to be a minor difference.

Which of these two models is the better choice for watching movies and listening to music, offering the best surround sound quality when paired with the Bear 2 soundbar + Apple TV 4K?

SONOS SUB Mini or SONOS ERA 100 x2?

Which do you recommend?

The sub-mini does not provide surround sound, only low frequency reinforcement. 

You have to decide which is more important to you. Or, both is a good choice.

Which do you think is better: Sonos One SL or Sonos 100?

The Era 100

After purchasing the Era 100, should I configure it in the SONOS app with the beam 2 soundbar as stereo or surround sound?

Depends on your intended use of the pair. My recommendation tends to be as surround speakers, but it still boils down to you, and how you intend to use them. 

​@Alec 33 

It appears you joined this thread as an interested party. I just want to make sure you fully understand the ramifications of your question.

I’m going to proceed on the assumption that you have (or will have) purchased two (2) Era 100’s speakers. You cannot configure one (1) Era 100 as a surround. 

When setting up two Era 100’s with the Beam 2 all three are Bonded as a unit:

• The default configuration is Surround Mode
• The Era 100’s cease to be independent and will not show as a stereo pair in the app.
• They cannot be used as Bluetooth speakers
• The line-in function to accomadte a CD player or Turntable is not available. 

However, within the app you can designate that when sending Music to the Beam 2 that the Era 100’s play in Ambient Mode or Full Stereo Mode along with the Beam 2. After the Music stops the Era 100’s will default back to Surround Mode.

To further explain:

• Ambient Mode is still stereo but at much reduced volume level. The Beam 2 will be the louder of the three speakers. 
• Full Stereo Mode is also stereo (as the name suggests) but at a higher volume level mimicking two stand-alone stereo speakers. In essence all three (3) speakers (Beam 2 and Era 100’s) play at the same level.

I hope this helps.

I have the following setup: Bear 2 soundbar + Apple TV 4K
Today I purchased and set up two SONOS ERA 100s.
During the initial setup, the two SONOS ERA 100s were configured for surround sound.
How can I change it to stereo in the Sonos app?

You’d need to either remove them from the ‘room’ as surrounds, or, in order to support the Beam, set them to ‘Full’ rather than ‘Ambient’ in the surround settings for the ‘room’.