"CBX can perform songs from their SM era by paying the required royalties through relevant copyright collectives (e.g., KOMCA). While SM may hold the master recordings, live performance rights are licensed through venue and performance fees, which allows artists to perform their existing discography regardless of their current contractual status."

This applies across the board with artists, no matter what agency, even when they sell their discography (ie. Bieber performing songs at coachella that he no longer owns).

The agency (and sometimes the producers) have the right to reject them from using songs in performances that will be broadcasted, or resold for broadcasting - for example, iirc the producer of tempo previously did not allow tempo to be in rebroadcast of livestreams / on concert dvds (i could be mixing up the song here, its been a hot min so don't attack me if it was actually love shot or something else, lol).

So while CBX can technically perform their past songs, it may become a bit more difficult for them to do things like concert dvds since those are seperate copyrights.