I have 4 Sharp machines at home. 2 are humidifier+cleaner models. They do filter dust, if you look at the filter inside after having the machine for a while. Also these machines are found at many business hotels so they must work! lol
The large KC-850U does work a bit differently compared to the other 3 smaller machines. Those 3 react quickly to odour, and very sensitive even if the source is 20 feet away. It triggers the plasmacluster thing.
On the other hand KC-850U doesn't appear to react to odour, but very sensitive to dust. Say if I fold laundry from 3 feet away, it triggers the machine into high speed fan mode, even when it's freshly launder garment.
All the machines are low maintenance. For humidifier depends on water hardness. You may need to de-calcify or replace the evaporating media. Otherwise you vacuum/wash the outer screen filter. If the machine comes with charcoal filter you can wash that. Machine comes with a "clean filter" reminder light.
There is no smoker at my place. So the HEPA filter lasts for several years. I don't run it during the day when there is no one around.
The KC-850U I paid 300 CAD 5 years ago.