Particulates seem to be the easiest to remove -- much easier than VOC's and other gases.
My new furnace has a MERV 11 filter that I've been playing around with in recent days as we've had AQI close to 100.
I have an air quality monitor (that measures PM1, PM2.5 and PM10) in the house, within about 20 minutes of turning on the furnace blower, AQI of 70 inside the house drops down to less than 10, and 20 minutes after that, it's down in the low single digits.
I have a MERV 13 filter that I could put in the furnace, but I'm not sure I need it since the MERV 11 seems to handle it.
Certainly not professional level calibration, but shows that it's within the ballpark. Unfortunately I don't think there's an official EPA monitoring station within 10 miles so I can't really check it against a calibrated monitor.
I aspire to have zero particulates in my home air, it takes some doing. Much of the particles are of human/industrial origin anyway. Exhaust and tire particulate and various broken down human built materials. (and an overabundance of human pieces that fall off and collect in ways that wouldn't happen outside)
I also aspire to have a low CO2 PPM inside, this conflicts with the previous (i.e. it is difficult without intense forced air exchange with the outside to achieve CO2 levels less than twice outside levels.
But to the contrary, I do not use disinfectants ever except in very specific circumstances. I go out of my way to not buy products which make disinfectant claims.
I think human beings need to be out in nature, to regularly come into contact with living soil. Not just "nature" of curated footpaths and manicured, fertilized lawns and parks, but actually getting dirty outside where other organisms live. It's hard to do in cities, and growing up on a farm it still seems absurd to me that I have to aspire and do great organizing to find myself somewhere in a city where I am not standing on a surface that has been engineered by people. The closest I can get is usually the strips of grass along the sidewalks that act as nothing but dog toilets. (I love dogs, but city dogs offend me. They're animals, they want to be outside and not just tethered to you or for the occasional adventure to a park)
An somewhat gross anecdote:
Several weeks ago I got a cut on my foot from some shattered glass that developed into an odd looking infection with red stripes/blotches that I was on the edge of scheduling an appointment for a doctor. I happened to visit a local lake and dipped my toes in for a bit. The next day I was amazed, the redness which had been growing in intensity for a couple of weeks was just completely gone. Maybe it was a coincidence but I strongly believe that whatever was having a grand ol time eating my foot seems to have made a tasty meal for whatever cocktail of microorganisms were hanging out in that lake (I assume it was a fungal infection which was outcompeted by a restored microbiome seeded from the lake)