Replication protocol vs replication functions

I am using Postgresql's logical replication in my application with the
test_decoding plugin. I am trying to understand the difference between
replication protocol and replication functions provided by Postgresql.
Specifically, CREATE_REPLICATION_SLOT call returns a snapshot name, but
pg_create_logical_replication_slot does not. The driver I am using does not
support replication protocol, so I am trying to use the functions. But how
can I retrieve the snapshot from the function call?

Can I use a combination of pg_export_snapshot with
pg_create_logical_replication_slot to get a snapshot of the open
transaction, that I can then use with pg_dumpfor example?

Thanks.