API endpoint testing with JMeter

I have an API endpoint (get request) that queries from multiple RDBMs, does some post processing, and returns a result. I’m refactoring that code to instead query from one columnar database. I went to test the improvement of the API through some load/stress tests. What is a good test plan to do this, I’m not too sure how I should configure the thread users, loops, and other parameters to effectively test.