I think it is very rare to find a viable bare-naked virus floating in air. The virus is in a small water droplet. Maybe a small snot droplet if you count all the stuff that comes along with it.
It is only necessary to filter the droplets out of the air to get protection, and the N-95 masks do that.
In a cough, the regular flu virus is on about 50% of the particles larger than 0.3 microns (the limit of the N95 mask). So a N95 (properly worn) will protect you from those. It doesn’t make you invulnerable, but it helps reduce the viral load.
And as you said - there is debate as to how viable a virus is by itself or floating on a small speck of dust.
Not about SARS-CoV-2 but these two studies convinced me to wear some type of mask.
The first is about household transmission of influenza-like illness from a sick child to an adult with or without a mask. There are caveats but in the household, at least:
“We estimated that, irrespective of the assumed value for the incubation period (1 or 2 days), the relative reduction in the daily risk of acquiring a respiratory infection associated with adherent mask use (P2 or surgical) was in the range of 60%–80%.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662657/pdf/08-1167_finalRCME.pdf
The other found no significant difference in the incidence of influenza between health care workers wearing N95 or Medical(surgical) masks.
https://jamanetwork.com/journals/jama/articlepdf/2749214/jama_radonovich_2019_oi_190087.pdf
I’ve decided to use a DIY mask made from a double layer of cotton t-shirt with some sort of filtration material in between. I’ve worn mine a few times, and it’s been comfortable enough. I’m undecided on the filter. I’ve only used a double layer of paper towel so far. Blue shop towels are supposedly better, and I have a MERV 12 air filter sitting around that i may decide to tear apart.
I may end up getting COVID-19 eventually anyway, but i’m hoping some sort of mask may reduce the viral load.