Have you tried downcut V bits? I fond that they do an excellent job of preserving details. However, I usually have to run the V Carve a second time to clean up the bottom of the cut.
Most V bits are shear cutting (cutting edge parallel to the shaft). The downcut V bits I use come from Cadence Manufacturing (Cody’s CNC):
He has 30, 60 and 90 deg V bits, the Groovee Jenny series.