The final version of the documentation for Maya is still under construction. This temporary version is based on the Blender documentation, though its contents is relevant to Maya as well (both variants use the analogical UI).
Advanced Packing Options
In order to access advanced options, expand the Advanced Packing Options subpanel:
Pack strategy
The pack strategy options define the scheme how the islands will be packed into target UV boxes:
Particular strategies are presented in the video:
Other functionalities
Other advanced packer functionalities provided by the packer: