MySQL Master-Slave setup: master is not indexed and slave is indexed
yes.

But 1) you have more trouble later on when doing maintenance on the tables (replicating alter statements might caue issues) and ypu might have issues when havin primary/unique/foreign keys on slaves only as it could reject data the master accepts

And 2) Slaves still have to insert the data and build indexes, yes the maser has a tiny bit less work, the overall system not, though.