Nexus 5X Project Fi

There is no different between the Fi version and the one from the Google. I believe Google has a clause in the purchase that requires you to activate the Fi service to get a refund on the purchase price of the device.
 
Can you buy one of these phones then use a normal sim.
I was looking into getting the 6p with the Fi offer. It turns out, if you buy through Fi, that's where you get hardware support should you need it. If you buy through Google Store, support comes from them. You can get the credit either way once Fi is set up. However, it seems (google product forum https://groups.google.com/a/googlep...forums.com?utm_medium=email&utm_source=footer) that support from Fi is more of a challenge once you deactivate the service. Hopefully, you won't have any issues. We have a 5x with no problems. Just check into it.
 
If you pay in full and get Nexus Protect, you should be OK outside of Fi.