Welcome--
I get it--it's tough to try Graphene (as you need the a supported Google phone--and they're not cheap) so it is a leap of faith...but if privacy is a concern, it's really the best game in town.
But yeah--buy a new Google phone and you're going to wipe it and install a new OS without even turning it on? Certainly a leap of faith... 😃
Ping me if you ever have questions or need help--happy ro help if I can!