Yes, “error” or “precision” might both be improvements!
As far as specific ways to figure out accuracy, I do all my observations (which aren’t many) by hand and err on the conservative side (ie, larger values) - sometimes taken with a GPS, sometimes with a friend’s phone, sometimes done from memory+maps.
There are some other forum threads that would be more useful for using devices/bulk adding accuracy:
https://forum.inaturalist.org/t/improving-location-accuracy-on-observations/1767
https://forum.inaturalist.org/t/set-location-accuracy-for-all-observations-together-when-uploading/15148/1
https://forum.inaturalist.org/t/gps-accuracy-not-captured-when-uploading-photos-taken-with-a-camera-with-a-built-in-gps/18861
https://forum.inaturalist.org/t/how-should-you-set-accuracy/16040
https://forum.inaturalist.org/t/geotagging-photos/66