(Character Variations) I know this doesn't work for 2.8/2.9 but...
CG think you should update the files for 2.9 at least, even if you don't update the vids as people will figure out the differences in versions.
For anyone on 2.9, yes the Character Variations don't show where explained in the viewport menu however you can find all the Character adjustments in Bone Properties > Custom Properties. Just fiddle around with them and you'll work it out.
Each set of properties changes when either clicking on that weird stick figure thing to the right, so head, body or colour.
I've not figured out the groups thing yet, but tbh I'm here for the animation side not so much the functionality of an old Rig file.