Hello. new to forum and was wondering if it is necessary to first set up my new pixel 7 pro (as in logging in with Google I. D.) prior to installing the new grapheneOS? I'd prefer not have fingerprints on the phone prior to install. Thanks in advance.

https://grapheneos.org/install/web#prerequisites

It's best practice to update the device before installing GrapheneOS to have the latest firmware for connecting the device to the computer and performing the early flashing process. Either way, GrapheneOS flashes the latest firmware early in the installation process.

Not mandatory but recommended. You do not need to log in to any account to finish the first set up, nor to update the phone to latest version of Android.