>However, there's also a chance that a virus can be exhaled immediately after getting breathed in.

Right, If exhaled immediately after breathing it in, it never deposited in your respiratory system to begin with.

Particles in the 0.3 micron diameter range are very evasive. They can follow stream lines around obstacles and they are too big to be influenced by diffusion (random motion of air molecules) so air molecules cannot "bump" them into a surface.

A droplet nuclei carrying virions in this size range could be inhaled and exhaled right back out. This size range is what an N95 is designed to filter out 95% of the time. For particles larger or smaller than 0.3 microns, an N95 filters more than 95%.