Yes, if you want Nexus Protect (the Google Insurance) order through the Google Store so you can add the insurance on, and order the SIM card from Project Fi. This is also the way to do it if you want the Ice color, since Project Fi is out of that color. After you activate the phone on Project Fi they'll refund the difference in the price you paid and the Fi price.
If you just want the phone (either white or black) but no insurance, it is easiest to just order through Project Fi, since you won't have to wait to get money back.
As far as Project Fi, as mentioned, the minimum monthly payment is $30. When you start Project Fi, it will start service but won't charge your first month's service for about 10 days -- it always is about 10 days behind between the start of your month of service and the payment date. If you quit in those first 10 days, I'm guessing they still charge you for the first month of service and then refund the unused balance (though it sounds some here will be able to tell us for sure).