Can I change the wal_level from logical to replica? If so are any impact on the replication process?
If you reduce wal_level to replica, and you have a logical replication slot (as is needed for logical replication), the server will refuse to restart.

This is because wal_level = logical is required by logical decoding and logical replication.

If you first drop the subscription and the publication, thereby removing logical replication, the replication slot will be gone, and you can reduce wal_level.

To switch from logical to physical replication, you have to re-create the standby server with pg_basebackup.