If you want good filters that actually clean the air you breathe in your RV, go to RVAIR.com. They make filters for just about all AC units. Mine uses the little round ones. Amazing how dirty they get.
If you are outdoors most of the time, it may not matter, but if you travel a lot and live in the coach most of the time, the inside air quality is much better with good filters.
We sometimes stay in areas where horse and cattle are nearby, and the filters keep the odors manageable. Same applies to campfire (and wildfire) smoke.
Amazon also carries the filters.
HTH
Tom