In all my years in development, I don't think I've ever encountered a Project Manager that had previously been a developer. Project Manager is a fancy title but PMs usually are paid less than developers. However, a sr PM may earn more than a jr developer.
PMs don't require any coding knowledge, their job is is keep track of the project itself, your description of what you enjoy fits in pretty closely with a PM, "... managing the workflow, making sure that someone else (or me) is doing a good high-quality job. I'm good at noticing problems early (hence thinking of improvements), preventing them from happening. I enjoy creating strategic layouts and plans on how to achieve a particular goal." PMs need to be able to identify project bottlenecks and critical issues so that they can be managed to complete the project on time without compromising quality.