In my opinion, the Google Pixel with GrapheneOS is considered the gold standard in terms of security and privacy. While I am not fully knowledgeable about its capabilities, it offers a comprehensive suite of security features.
The iPhone is also a viable option. You can easily swap between iCloud to a more secure encrypted provider for both cloud storage and photo backups. Additionally, any notes application can be replaced with a more secure alternative.
Samsung phones can support a range of operating system images that can be flashed, including LineageOS. However, I am not fully aware of all the available options.
Is the open world mechanics massive on it?, I mean in terms of hidden details and basically lots to explore?