We've been gathering industry reports and scientific research around the effectiveness of different types of personal filtration equipment, and we hope this list helps inform you a bit better.
3M published an informative PDF describing the different types of filtering facepiece respirators. As a large producer of N95 masks, they have an obvious incentive to promote their products, but this PDF is still helpful in describing the differences between global standards for rating PPE.
Smart Air Filters blog has an informative post comparing homemade masks to manufactured ones (such as KN95s). They show that while a homemade mask is better than no mask at all, they are not as effective or as durable as an authentic KN95.