In the wild my cat would eat 100% live.
Yes, she hunts and eats mice as a domestic pet. I can't do anything about that. If I see her with one I take it away. Prolly it dies anyway ...
Do I feed my cat live mice? No, she eats wet and dry cat food.
My snake eats dead mice. Maybe if the snake was ill and would only eat live I would try. But it eats dead so no worries.
I don't quite get why you would prefer to feed a live mouse.
My thing is - if the snake (or cat) was in the wild, it hunts its prey. The mouse gets away, or doesn't. If it doesn't, for sure it is in pain, or scared. THAT is nature.
But putting a live prey item in a cage with a predator, it CANNOT get away. I don't see what is natural about that. If it can't be avoided, then perhaps you weigh the life of the snake or the life of the mouse.
But if it CAN be avoided, really, why?