Google Pixel (Verizon and GSM)(S&D)

how do I select that I want a GSM unlocked one ? and the exact version ?

This is a Verizon phone that is unlocked for GSM. You don’t need to choose for that.

I feel stupid asking this, but will this work on Google Fi or Sprint? Thanks to anyone who replies.

According to Wikipedia, there are only 2 types of Pixel phone: G-2PW4100 (North America) and G-2PW4200 (International). I am certain that this is the North American version, which IS compatible with Google Fi and Republic Wireless (the international version does not have CDMA and therefore is not compatible). Pixel XL is an identical situation, just with different model numbers.

Sources:
https://en.wikipedia.org/wiki/Pixel_(smartphone)
https://support.google.com/fi/answer/6224695#supported_model