This sounds like questions about a proprietary service from AWS. You are probably better off directing your questions to their support, as they have a lot more experience with it.
Recently we tried to migrate EC2/Postgres with Master/2Slave (Streaming Replication /Hot_standby) into Native RDS based server. But while we try to use Database Migration Service, our aim is to use one of slave as SOURCE for DMS , So AWS/DMS requires that in source machine to be with two parameters changed - max_replication_slot > 0 & wal_level = logical. If i change those parameters in Slave, will the master will recognize slave with Logical streaming? Am not sure master with Streaming Replication(Physical) will Sync with Slave with Logical Replication?
Also if change physical streaming to Logical Streaming, will there be any change in data blocks or data in postgres?