upgraded from a Pixel 7 to a Pixel 9 today :-)
one observation: the P9 is slightly smaller than the P7 :-)
like always flashing GrapheneOS on the P9 was super easy. Used the P7 to flash the P9 :-)
At first it could not find the P9 usb device, that was user error, I had the USB security settings set to charging only after chaging that to all it worked immediately :-)
sat down a couple hours to set the new phone up and backuped all my pictures to my PC.
banking apps made no trouble at all. they work on both phones :-)
going to live with both phones a couple days just in case I missed something important to transfer.
then I am going to factory reset the P7 and set it up for my mother. upgrading her from an old moto phone to the P7 with GrapheneOS.