I've been casually researching books on viruses that I could find free pdfs for and searching the term "mask" in them (checking of course that they were books related to airborne flu or coronaviruses, and not computer viruses) and quite frankly... most of these books don't even contain the word "mask" anywhere in their text, or at most just have a vague recommendation to use them in a laboratory setting with no mention of their actual effectiveness.
I did find out that coronaviruses are between 200-400 nanometers big (for reference a human hair has a width of 80,000 to 100,000 nanometers and most cloth masks can't even stop hairs), the first virus was photographed with an electron microscope in the 1940s, polio was photographed in the 1950s, and that use of masks in hospitals became common to protect against bacterial infections in the 1920s and even then they recommended that they replace masks frequently, and that mask mandates during the spanish flu were basically ineffective.
Now I don't have access to current medical textbooks, but if masks are so effective and proven you'd think that any book about airborne viruses would mention mask use and how effective they were... unless masks were not effective against viruses.
For example: Methods in Molecular Biology 1282, Coronaviruses Methods and Protocols (springer protocols) a textbook on coronavirus copyrighted for 2015 (299 pages) Has the word "mask" once, but it does not refer to medical masks, but rather "masked" in how the virus infiltrates a cell. It has a fairly long section on "prevention" but it doesn't mention masks at all.
I asked the same things (N95 vs cloth). The best explanation, came from Dr Drew. He said a N95 was best, but even if you didn’t have one, any mask would do. A big reason he cited was touching your face (nose / mouth) with hands. The mask doesn’t allow you to directly touch your face, which can be a key way for entry into the nose/mouth. I’ve also heard the virus does not float on air alone, it needs water droplets to travel. While only an N95 can keep out the virus, any tight cloth can provide a better barrier against larger water droplets. I still only wear N95s & believe that a lot will come out years from now. It may not be as simple as wear a mask / stay home.
There is scientific evidence that N95 is effective at filtering SARS-COV-2. There is no scientific evidence that cloth or surgical masks are effective.
This is as simple as it gets regarding mask filtration and effectiveness.
Obviously touching an infected surface and then touching nasal membranes or eyes can be a route of infection, but that is not exactly relevant to the mask discussion.