Additionally potential differences tend to attract rather than repel unless these individuals were also charged with the same polarity as the field as far as I know.
Wearing a conducting ring might make it easier for charge from the air to move into your body through your skin - but it will not make it easier for that charge to get to the floor (and then to ground) from your body.
Most shoes are not great insulators - they insulate but how knows who much. electricians sometimes buy special shows that do insulate. Those shoes come with care instructions and dust on the outside compromises their insulation.
The care instructions and dust you mention sounds likely to be super important when you're casually touching live stuff while standing on a grounded floor.
In an electrostatic situation, the electrons can flow (almost) freely without the shoes / tyres and so a large differential between body / ground will not build up. With shoes, you'll need a large difference to build up (10kV? 20kV? More?) before it discharges.
Anyway, there is clearly a difference between these situations - even if the shoes don't provide magical protection. But the shoes are not magical, as you correctly describe.
Which would likely make you a pretty nice load or resistor!
After piercing the skin, the test current from the multimeter (9v) was sufficient to electrocute this person. Sadly it (apparently) was a fatal injury. I couldn't find a reference, but the logic makes sense (50V sufficient to kill normally, skin is most of the protection).
When dealing with electricity, having items which reduce the protection your skin offers (metal rings, moisturizer, etc) is a substantial risk.
When insulated, there is no difference. Your potential is “floating”.
If the body is insulated from ground, the body is at the same potential. No current flows. No material conducts anything :)
For the same reasons, high voltage repairs can be done live from a helicopter: https://m.youtube.com/watch?v=9YmFHAFYwmY
Around 1:10 you can see the lineman connect the mains to the helicopter, to neutralize any potential difference.
After that, the lineman and the helicopter are at the same potential as the cable, so no current flows.
If someone dropped a line from the heli to the ground however.. zap!