I don’t know about Top Writer status, but here’s the proof that Membership isn’t needed to participate in the Partner Program:
Do I have to be a subscribing member to participate in the Partner Program?
No, you don’t have to be a paying Medium member to join the Partner Program and earn money for your writing.
Right from here:
https://help.medium.com/hc/en-us/articles/115011694187-Medium-Partner-Program-FAQ
