EX300 is RHCE that was released on RHEL7.
EX294 is RHCE that was released on RHEL8.
They are both RHCE but the former one is being retired, since Red Hat are upgrading their exams to RHEL 8. If you pass EX294, you will be RHCE on RHEL8.
Yes. The new RHCE title can be acquired by passing the EX294 exam.
But if you wish to learn the contents covered in RH300 and also learn to automate the same using ansible, I highly recommend that you learn RH358 - Red Hat Services Management and Automation.