Malakai unless I'm mistaken, it can be restored to any device with Seedvault. I don't think there's anything special about the way the app is installed on GrapheneOS that makes it incompatible with others.
It uses an old Android API for backing up data. I don't know of all the details, but if an app opts in (or if it doesn't opt out, I forget), then files can be backed up. It can back up all (or some, I forget this too) files the app has saved internally, for example login info. When restored to another phone, that data will be seen by the corresponding app on the new phone.
All that said, keep in mind that Seedvault isn't the most reliable, so some data might not be backed up, or other data might not be restored. There are options to back up files stored on the phone and to back up APKs, but I've read that sometimes those don't happen either. Just something to keep in mind.