I'm currently using GrapheneOS and I quite like it, but I would like to switch to something else. Will I lose much privacy if I switch to e/OS? Can I lock bootloader after flashing it like on GrapheneOS? I'm using Pixel 7 btw
It does not "already have google code in it". That's an optional, tightly scoped feature with one specific blob that is required to implement the SafetyNet feature in any implementation
I see no reason why you couldn't run µG inside a sandbox too; the differentiating factor for security is the sandbox, not the GMS implementation. Also has nothing to do with privacy as, contrary to the original GMS, µG doesn't spy on you to begin with.
I recommend sticking to GOS. If you'd like to use something else, I'd recommend DivestOS. CalyxOS, LineageOS, /e/OS and iodéOS are all significant downgrades in usability, privacy and security and therefore not worth using on a Pixel.
you'll definitely be loosing security, which can turn into loosing privacy if you get affected by malware.
you'll also be loosing privacy if installing proprietary apps, since GrapheneOS has features like storage scopes and a better permission system that help minimizing privacy issues.
I think that locking your bootloader in a Pixel is possible regardless of the ROM you install.
Anyway, I think that there's no real benefit of installing any other custom ROM in a Pixel other than GrapheneOS. You'll be just loosing out in security and potentially privacy for no real reason.
/e/ includes microG per default and thus calls google servers. /e/ includes unique identifyer per update call tracking its users. Graphene uses several proxy servers to hide user information, /e/ does not in similar way. And so on...
☝️ this is correct. GSF calls home and /e/ is a different beast. The founder of Murena and /e/ is on Fedi so you could drop him a message on Mastodon and see how he answers.