Lemme make it clear:
Protege has power mimicry on steroids, he can copy any powers/ abilities as long as he observes them in action.
According to Wiki, he can copy a person's abilities as long as the person is using them at the time. However, he can't copy a device's/ gadget's ailities, what he copies is the user's skill in using the gadget/ device.
However, we saw Jack copy the power of a taser early on. I'm under the assumption that that was simply an error or a plothole since Protege's powers are more than sufficiently OP.
Thus we have the term Infinite Copy
Then we come to the second part of Protege's power mimicry where he does not copy a power on the scale of 1:1 but to the level he wants. The guy is said to reach a level of omnipotence on his own, which he does when he copies Beyonder's and Living Tribunal's powers before he's sealed.
This is most likely what the author meant when he coined the term "Infinite stacking/superposition."
I hope this clears up any confusion.
I have to say, from the little I read about him on wiki and fandoms, that guy is broken!!!