mysql replication using galera
For your first question:

Multiply Things you must know before using Galera Cluster.


Galera Cluster is not for scale write
Galera Cluster is not load balancer. It must integrate with HA Tools for this option
It's virtually synchronized Multi-master Replication
You need minimum of 3 nodes/servers(or 2 nodes and 1 abrirator)  to avoid split/brain.
You can't use MyISAM all of tables must be InnoDB.


So if you want to use Galera Cluster I thinks this article is good for start.