The latter is definitely possible. Back when I was still playing RPS as a kid, I was fairly good at it; enough for somewhere upwards of 70% of my plays to be wins.
You don’t want to change your move at the last moment though so much as you want to keep your hand in a plausibly formless configuration you can turn into a move at the last moment. Less likely to be called out for cheating.
The latter is definitely possible. Back when I was still playing RPS as a kid, I was fairly good at it; enough for somewhere upwards of 70% of my plays to be wins.
You don’t want to change your move at the last moment though so much as you want to keep your hand in a plausibly formless configuration you can turn into a move at the last moment. Less likely to be called out for cheating.