Phosphorius pretty sure you won't be able to use Google switch (or Android Switch). I also first moved from Android to GrapheneOS. Here's what I did and I'd recommend that anyone else does thats new to this (and yes, its going to take longer to switch to GrapheneOS than a 'regular' phone since you can't copy your old phone to the new one easily).
#1 Install all the apps you think you'll need on GrapheneOS. This includes weather, email, app stores, Play Store (if you desire) and any other apps you think you need. It'll make it easier to transfer all your data over - trust me.
#2 Prepare to move stuff to your GrapheneOS (GOS) phone. You can do this 1 of 3 ways. Back up your files, photos/videos, and audio to a flash drive, connect both phones to each other and transfer from old phone to new phone (I did this method), or plug both phones into a computer and transfer that way.
To export your contacts, go to settings in the contacts app and click 'Export'. Export them to a .VCF file. Transfer this file to your phone. On your GOS phone in Contacts, select 'Import' and choose the file from your files when prompted. FYI, you can delete the file when you've imported them. For text messages and call logs history, I used this app (install on both phones).
https://play.google.com/store/apps/details?id=com.riteshsahu.SMSBackupRestore
Just back everything up once and follow the instructions. You'll end up with a file that you can import using the same app on your GOS phone.
Hopefully this covered most of what you need to know for switching phones. If I've missed anything or you have any more questions, let me know and I'll try to answer them! :) Good luck!