Can PostgresSQL cluster have synchronus and asyncronus standbys at the same time for the same dbs?

In this question, https://dba.stackexchange.com/questions/267400/write-concern-in-postgresql/267407#267407 Laurenz Albe explained how to control the set of standby servers when data is committed to PostgresSQL, and that gave birth to another question. What if I want to have N standbys, and want to have synchronous replication enabled for some M subset of N, is that possible? A use case could be a cold backup. I don't care of data inconsistency for N-M subset, I just need to have that on M subset of N standbys.