The following tools would help you for measuring the performance of your server and test the MPM Settings values of your Apache.
Apache2Buddy is a great tool that checks your server setup and performance and makes a report and suggestions based on the information it collects. It calculates the MaxRequestWorkers on remaining RAM, not total installed RAM.
You can run Apache2Buddy by using the following command:
curl -sL https://raw.githubusercontent.com/richardforth/apache2buddy/master/apache2buddy.pl | perl