> I was running the database on the webserver previously but moved it to its own server. I have subsequently deleted the old database there since this last reading.
What is the purpose of those outdated htop screens then?
> Which machine is likely to consume more memory? The DB server or the web server?
You can not treat a specific (running) server stochastically!
> I have been over that performance doc. Im using opcache.
What are your findings, other than that you use Opcache? Did you see this simple https://moodle.org/plugins/report_benchmark ?