Right now, you're offered the choice between master+agent and agent. We could also take the time to briefly explain what each choice means and in which scenario the different choices would be useful.
We should consider making the choice more user-friendly. We could, for example, begin by offering a choice between a type of installation, “Single server” or “Cluster”. If the admin chooses cluster, we could then show 3 new choices; “Both Master and Agent”, “Master”, and “Agent”.