I do this often.
Set up a test webinar. You can actually copy the real webinar to make a test webinar. When I do this, I add the word TEST at the beginning of the webinar title, so I can remember later that this was a test, not the real webinar.
During the test, you can check microphones, webcams, and having the presenter share their screen.
On problem I have found is that folks will test their system, then between the test and the real webinar they decide to get a new microphone, webcam, or even a new computer, and now for the real webinar we are troubleshooting their system. Tell your presenter that they should not change their computer hardware after a successful test.
Hey Chris! My customer is just an attendee, not an organizer. He knows about the system check but he says zoom has a site where you can go to make sure you will be able to join before the meeting takes place, so he was looking for us to implement something like that.