The problem is most masks don't actually protect the wearer. If we had them in sufficient quantity, the public health advice would be to wear fit-tested N95 or better particulate respirators.
That was that thinking in April, but more careful studies are showing that wearer protection is quite high. And that bandanas and neck gaiters do actually offer reasonable protection.
Here's the preprint from Linsey Marr who is considered by many a leader in aerosol risk.
I think resistance to air flow is probably enough to evaluate whether a given package is better than cloth masks though (if the KN95 resists flow, probably better).
Right, which is why it's so vital that cloth masks be trivially easy and cheap/free, so that I can be confident that everyone around me has access to them
