Plex Pass is required to control Sonos from Plex apps, but music from your Plex library can be played using the Sonos app without Plex Pass. See Control Sonos Playback With a Plex App | Plex Support
If you have hi-res audio files you’ll want to check supported audio formats at Sonos Support
I have some issues with the play queue, but only in atypical usage scenarios and nowhere near as annoying as unwelcome gaps during albums. See: Plex for Sonos - Queue (mis)behaviour
And either write album gain values to track gain tags or avoid using replaygain tags.
If you have the financial capacity you could potentially purchase a Port (successor of the Connect) directly from Sonos, assess the suitability, then pick up a used Connect and return the Port free within 100 days.
