- Edited
jb7 "I've contacted one supplier of degoolged phones and they have told me I can do that but would be a waste of money"
I mentioned this to you, but I wouldn't buy from this person.
This question isn't really answerable, I don't think you really understand what you are asking. Privacy isn't a defined concept, its just exercising sharing what you wish to share and withdrawing what you wish to not.
Whoever is the vendor of those phones has a seriously flawed idea of privacy and more importantly probably doesn't know what he is doing and may sell you an insecure and non functional phone.
Setting up GOS takes 20 minutes, buy a pixel from google themselves or your local electronics store (make sure the pixel is carrier unlocked).
After that, simply consider what you do, and don't, want shared. GOS makes it easy to control app permissions (well, android in general but GOS has more options and security features)