Settings for cluster nodes

Elastic Stack Elasticsearch
1

I have 3 nodes.

How do I set discovery.zen.ping.unicast.hosts? Do I set all of the host names for all nodes into the config file for each node?

Do I set node.master: true for 2 of them or 1, to avoid split-brain?

Do I set node.data : true for 2 of them or 1?

What should I set for discovery.zen.minimum_master_nodes? 2, or 1?

The documentation leaves me a confused as what to use.

2

The unicast list is a seed, I'd put your 3 nodes in there to start.
You should set all 3 as master and data nodes, with min masters as 2, as that is a majority.