Having 2 master eligible nodes in a cluster is a bad idea. You should always aim to have exactly 3 so two nodes can elect a new master should one fail or leave. I would therefore recommend that you set up 3 equally sized nodes that hold data and are master eligible. In addition to this you can use a coordinating only node with Kibana.
With this setup, you would direct indexing operations at the master/data nodes.
If having 3 data nodes is not an option, I would recommend setting up the cluster with 2 master/data nodes and one smaller dedicated master node. In this configuration you would send all indexing request to one of the master/data nodes. In addition to this you can use a coordinating only node with Kibana.