What's the recomendation when dealing with a index widely used?

I have plans to centralize the indexes I use for a few reports. The plan is to have an index with little more than 2million documents; Short in size but still growing and is also highly searched within multiple Kibana spaces.

The reason for that is that we need to have a single index to access via PowerBI.
With everything in mind, I've been wondering if there's anything else I could do to enhance the health of this centralized index.

I'm quite new to Elasticsearch by itself so I'll gladly acept any tips regarding the indexing process.