A:AnswerGen. 4 Sub has a faster CPU, more memory & upgraded wireless hardware including Wi-fi 6 support. This gives it smoother performance, and more headroom for future Sonos updates. Both deliver the same deep clean bass down to 25Hz. Sonos didn't change the acoustic signature, the improvements are mostly in efficiency and system performance.
A:AnswerNo. The sub plugs into the wall for power and must be connected through your Wi-Fi to link to an appropriate Sonos product. There is an input for a wired Ethernet cable connection and an HDMI cable input to connect to the Arc or eARC connection on your TV.
A:AnswerThe button is for joining (pairing) your subwoofer with the soundbar. The subwoofer powers on without having to press a button.
https://www.sonos.com/en-us/guides/sub