They are all you, until they start reacting differently to their different inputs and anything stochastic within their simulation, and at which point they stop being "the same" you is basically up to you. The difference between them after a minute or two would probably be nothing compared to the difference between you and you a year ago; if you call the latter "you", the former should probably count too. You wouldn't be aware of being 100 beings, but 100 yous would be aware of existing.

Calculating down to the quantum level is hopefully not necessary (that seems impossible to get efficiently out of any computing substrate physics will let us have). The few people suggesting that physics at that scale impacts consciousness aren't taken very seriously by neuroscientists in general.