Quick back-of-the-envelope calculation suggests that merely standing an extra foot away above the 2 metre recommendations might make as much as a 25% difference in viral exposure*. Clearly a top-of-the-range mask, if properly fitted, would beat that, but it's hard to assess what happens if people worse face masks incorrectly fitted, or not made of the proper material, and then ended up standing closer more often.
These are clearly difficult calls, though, and I'll obviously defer to government advice as and when it comes, or to any study that demonstrates that my pessimism here is unfounded.
*Optimistic application of inverse square law, which seems reasonable here.