GPS versions

Is there a noticeable difference between the versions that Garmin has now released for the Fenix 6 ?
So the newer ones from 5.50 > 6.30 > 6.60 ?
Was there but only some time ago the merger of the versions and shortly thereafter they were separated again.
Now again pushed to 6.60.
And from the perhaps noticeable or the more accurate tracking apart, would also work the 6.60 on older FW ?