Approval of membership before payment ?

On a website for a motorcycle club new members need to be able to register and choose a membership type. After that an admin needs to approve them before they can become actual members, and then they would finally need to pay the subscription - is that flow possible with CBSubs ?

Yup, that's doable. Edit your plans and under Workflows set "User Approval by Moderator" to "Yes, before payment (override CB)" to require moderator approval before collecting payment.