You always have to match the grid created by raster_to_geology in krig_3d_geology, not the other way around.
raster_to_geology can only crop and/or subset the grid that you are starting with.  It cannot create a finer grid or rotate the grid.  There is little flexibility.
The actual resolution is reported to the Output Log when raster_to_geology runs.  This resolution accounts for any cropping and/or downsizing that you have set.  For example, if we open the sample application in Studio Projects – Reference\grid-cut_surface.intermediate.evs, it reports
 which is a grid (nodal) resolution of 397 by 243.
Next we would need to know the extents of the grid, which is the Xmin, Ymin (Grid Origin) & Xmax, Ymax (Z extents are irrelevant for krig_3d_geology).
There are several ways to get this, but the easiest way (with the most decimal places) is with the statistics module.  Connect statistics as shown below:
and it will report its results to the Information window, with the numbers we need shown highlighted in yellow.
Now that we know what’s coming from raster_to_geology, we build a grid in krig_3d_geology with EXACTLY the same extents and resolution.
Usually it is easiest to do this with this with the Rectilinear gridding option and manually setting the grid  Xmin, Ymin & Xmax, Ymax values to match the extents reported by statistics.
NOTE: When you manually set the grid extents, the Boundary Offset option (default 10%) becomes inactive.
If you do any cropping or downsizing in raster_to_geology, both the grid resolution and extents will change, and you will need to change the settings in krig_3d_geology.