DO180 has a fair amount of OCP, and so did EX180. It was a good Level one course and certification for OpenShift.
DO188 is mostly podman. I don't think EX188 is much of a OCP certification.
What is Red Hat's stand on the entry level OCP Certification now? EX280?
The ex188 it's an introduction to the container world with Podman.
It will be better to start with ex280 and ex380 If you are looking for Openshift platform administration.
Both exams complement each other by giving an intro and deep dive inside Openshift as a Platform administration.