Depending on your computer power, may get framerate drop off at 1M, and some more complex functions seem to take very 5 minutes to compute, or some boolean operations may fail.
To reduce a triangle count:
Select>Edit>Reduce
http://help.autodesk.com/view/MSHMXR/2019/ENU/?guid=GUID-54087649-E962-409E-8565-F646BDA80B33
Not necessary though. Only use this if the above mentioned issues are interfering with your CAD work, such as in needlessly high res scans.
