But, what is the current replication setup that comes with postgres that is well documented with the PostgreSQL (current-version) documentation... the past, when I've looked there's mention of 2-3 solutions (none in-the-box) and others that require at least a 5-figure support contract.

Compare to MongoDB, RethinkDB, MS-SQL and others where the tooling for replication comes in the box. Yes, to of the examples are "no-sql" but even the mysql replication is in the box and supported as such.