Mask questions

Considering only their effectiveness at a) slowing the spread of covid-19 and b) protecting you from covid-19, in public and grocery stores and similar (that is, I'm not asking about bacteria, fungus, healthcare settings, etc.)...

• If an N95 mask doesn't quite fit as tightly as it should, is it still significantly better than all surgical & cloth masks? Or does the imperfect make it likely not much better than a surgical mask?

• I've seen it claimed that multi-layer cloth masks are better than actual approved surgical masks. I'm very skeptical. But is there some validity to this claim?

• Is there any difference between US N95 masks and Chinese KN95 masks for this purpose? Other than the fact that I've never figured out how to actually fit a KN95 to my face :) But aside from the fit, are they effectively exactly the same thing (for this purpose)?

If you have helpful references or sources for answers to any of these questions, I'd like to read!