Hi Nirbhay,
thank you very much for your answer.
This cluster is already in production, with few databases (for mail user authentication, radius authentication, and so on).
My question is:  what would will happen if I change wsrep_sst_method on one node?
How the other node can be "synced" if wsrep_sst_method is different (even for a few seconds)?

Thank you, regards