Hi @Andy, let’s have a look!
(Hope you don’t mind I updated your Google Drive links with links to uploaded videos here, so we can watch them without leaving the page. It also helps prevent eventual “link rot” such that future generations can still see them. You can upload videos here by drag-n-drop.)
From the time I wrote this, I actually made a breakthrough that will allow use of Live Mode transfer to rigs of any complexity in Maya. I wasn’t expecting this, but this does mean you will be able to pose arbitrary rigs, including IK controls, using Live Mode in the near future. Just FYI!
I can confirm this, this is a bug. The reason it’s happening is because of the default assets; they were originally made Y-up, and have a 90 degree rotation on their top-level group in the Outliner. It should not affect your production assets or any asset made with Z-up.
I can also confirm this will not be an issue in the next update. For now, what you can do with the default assets is unparent the root joint and now Live Mode transfer will work.
Very true; at the time of writing this, the wrench was very experimental and it wasn’t clear they should continue to exist or not. But we now know the usefulness of having pins active during Interactive Mode, so I’ve gone ahead and added the missing section now.
Ah haha, yes. Noodle fingers! Per default, the rotation stiffness of all Markers is set to 0 in Live Mode. Such that they don’t counter-act your posing. You can enable it using the Tense button on the right-hand side.
This will make the fingers (and arm) still respect the rotate stiffness, whilst still responding to your Pin Constraint and the magnet as you click and drag in Live Mode.
Hm, if you can reproduce this, let me now. Smells like a bug.
Normally, wiggling is the result of two or more forces contradicting each other. Like for example in that other post you found:
The hands couldn’t reach the face, because the head was responding to the rotate stiffness of the shoulders, torso and neck. Greater force being put on the hand to try and reach it resulted in even greater forces trying to push it away. So something to keep an eye on is to ensure there isn’t too many of those forces contradicting each other. Which is easier said than done, but should come with experience.
Here’s my favourite example of this in the wild. 
Eeek, yes please do let me know how I can reproduce what you are seeing. This sounds bad!
There isn’t anything at the moment because frankly, the technology was new to us as well. We have been exploring it ourselves to try and find a workflow to recommend, and have been listening to the community for what they can find. I’ll put together what I’ve personally found so far and maybe that’ll help. Stay tuned for this shortly.
Hope this helps, and keep posting updates about your progress, this helps push the progress of Live and Interactive Modes and is exactly what we need!