If a DEMs base elevation units are feet and the toggle specified meters, all elevations are converted when reading. This option does not change the base planimetric units of the DEM and you should make the elevation units consistent with the planimetric units in order to ensure that slopes are computed properly when computing basin geometric parameters. The questions are.
Lets assume they are meters.
The dimension of N can be specified as either 3 or 5, meaning that new elevations are computed from either the nearest 8 or 24 neighboring points. Or a combination of all these factors. The filter ratio should be between 0-1, and is used to specify the weight of the central cell of the filtering matrix. It can be used to establish how much effect the DEM point itself has on a newly computed elevation, and how much effect the neighboring cells have. I think that an illustrative example will help me to understand it.