With my CO2 laser, polycarbonate tends to melt better than it cuts as opposed to acrylic which cuts better than it melts. Great edge quality although some raising of the surface around the edges has to be expected with polycarbonate.
It does not take very much CO2 laser power to engrave / cut acrylic and 'depth of cut', 'power setting' and 'axis speed' are all tightly related so for engraving to a defined depth if the power setting is reduced to minimum and the engraving is still too deep then the axis speed has to be increased. If the engraving line width can be increased then defocusing the beam will also produce a slight reduction in power (but not much). Raster engraving is probably preferable to vector engraving in this instance and I think you should be able to achieve excellent results.
Tweakie.
CNC is only limited by our imagination.