Microsoft Certification Exams

I am attempting to take a certification exam (Microsoft Office Specialist: Excel Associate Office 2019) through the MC COOL system. The Marine Corps would be paying for the exam and to ease my ability to complete the exam, I was going to request to have the test proctored online since I'm currently active duty. I wanted to know whether it would be easier to use Certiport or Pearson's and how the Marine Corps and Microsoft coordinated and approved the scheduling as well as what steps need to be taken on my part after I submit the request form to MC COOL. Any other information on this subject would be helpful.