Will this NZXT Phantom ATX Case fit a Corsair H100i?

It fits the H100i fine, I don't know if it fits push pull configuration.
And also it has a good clearance for GPU's so you won't have any problem fitting those video cards in the Phantom.

Where would the dual 120mm fans go, I don't see clearance for it? Are you positive man or what?

You can probably do a push pull configuration with this case but you'll have to leave the 200 mm fan in the top (Between the top of the case and the plastic cover with mesh) and put the 2 metal brackets that your case includes to fit a radiator and do the setup.

Fan | Fan
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Radiator
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Fan | Fan

You can swap the 200 mm fan in the top and put 2 x 120 mm fans.