Yes, Beocreate is still maintained. The software has been merged into HiFiBerryOS. There is no seperate Beocreate software anymore. But the speaker profiles are integrated and you can still use these. While B&O doesn't work on adding more speakers, the profiles that are available (incl. CX100) can just be used.
Most CX50/CX100 will need new foam surrounds:
https://www.hifiberry.com/wp-content/uploads/2019/05/changing-foams1.pdf
Other than this, the CX100 is a great small speaker. Build quality is definitely on another level than today's small plastics speakers. With the Beocreate speaker profiles, it will provide more bass than the original. Still keep in mind that these are still small speakers. So don't compare these to a floorstanding speaker.
If you don't want to do the modification by yourself, I can recommend a partner who offers complete upcycled speakers.
Keep in mind that the whole system is based on the Pi and open source software. This means it will give you more flexibility than the Sonos. On the other hand, you might have to do a bit tweaking from time to time and services might fail as there is no official support from services like Spotify or Tidal.
