Only Exam 8 will be offered in Fall 2021 so taking a Spring exam during the Spring 2021 sitting seems the most logical to me. 7 is required to sign opinions, so I’d start with that one. After that you have more freedom to decide if the additional 2 exams are worth taking (depending on your career goals, company, etc).
I remember that when the Exam 7 syllabus changed significantly a while back some people were skipping 7 until they had a better idea of how the new content would be tested, but given that the content hasn’t changed for a while and we’re not getting any more Examiner’s Reports, there’s not really a reason to do that anymore.