Recommended server config for Varnish & Redis?

I am working on a Magento 2 site and need to implement Varnish and Redis to increase the site speed. We’re getting on average 500-750 visitors a day which may assist with the below recommendations.
The stack we’re running is: AWS EC2 running nginx, AWS RDS, AWS CloudFront
To implement Varnish and Redis, what would the best practice be out of the following:

• Install both on the same EC2 running nginx, and bump up EC2 resources as required, or
• Setup a new EC2 to run both Varnish and Redis, or
• Setup two new EC2’s and run Varnish and Redis on their own instance

Or, something else altogether?
Thanks!