Ideal AWS templates for Webpagetest private instance

What the default and recommended AWS templates for hosting Webpagetest Private instances to get consistent results without CPU usage having impact on results?

Presently, I am thinking of going with below

Server - t2.small
Agent - c4.xlarge/m4.xlarge

Are they overkill?

c4.large works well for the agents, no need to go to xlarge.

As far as the server goes, it depends on how many agents you are going to be running (and doesn’t impact the results).

This may help: