You will still see the Google splash screen on your Google Pixel device, because it is still a Google-branded hardware device. That said, once CalyxOS takes over as the operating system on the device during boot, all of Google’s software is gone and cannot collect your data and invade your privacy.
As to Google Services, the recommendation is definitely to say NO and to disable that function on setup. The use of Google Services will mean that all of the applications relying on and using Google Services by default can and will collect your data and send it to Google, which is absolutely what we’re trying to avoid.