+1 for the Q. Are there any questions I could ask from an agency to understand if they know what they're doing? Many agencies offer their services with wide price range, but I heard very mixed reviews of all the price segments.
I created a set of slides which introduced the project and created a doc with my expectations. I posted a very detailed job spec on Upwork, shortlisted 20 companies, and interviewed 10.
I picked the one I did because they were most transparent with what they would actually deliver. For me it was about a pre-launch strategy, what to do at launch, and how to systematize/scale post launch.