The machine I have does have an automated Z axis for doing inner carving. Yes, all the engraving I have done has been single pass and is amazing in quality. I can single pass cut 3mm+ plywood with basically zero kerf, having had several large Co2 machines the zero kerf with basically zero burning and zero kerf is amazing.
I am curious though, you said 1.5.8 has the point cloud preview (I have seen that on several videos) but it seems the newest version of the software is 1.5.7.6. I assumed the point cloud preview was on a previous version which I would actually like to try but I have never found a copy of what ever version it is that had that feature.