Thank you for the interest in NodeXL!
There are several ways to layout groups in NodeXL.
See the NodeXL>Graph Pane>Layout Menu>Layour Options menu:
In that dialog there are choices of layouts for groups:
You may want to experiment with these options.
NodeXL does not (yet) have a group layout that allows the user to select the order of their presentation.
Currently, in the Group-in-a-box layout, groups are ordered by the count of vertices located with them.