I do have a solution if one is experiencing "imposter syndrome" in a particular domain: have a mentor. The mentor will help you measure the extent of your knowledge. If the mentor says, "That looks/sounds good to me," then you cast the research into the big scary world and sit with those "imposter" feelings knowing they are false positives.
Eventually you learn to measure your knowledge without reliance on the mentor, and the "imposter" feelings lessen.