> "can someone see that I've installed an app"
You say preferences and you didn't say what you mean. One meaning of the word preferences: what if you installed Grindr?
Sure I use gmail, I've been locked in for 15 years. Someday I'll get fed up enough to bite the bullet and move off it.
Apple can push updates and change the rules on your device at any time. Rooted Android works better in that regard: you can still use Google stuff on rooted devices. Also I don't think Apple's security posture for users in China is better than every "other big tech co."
The takeaway for me is that Apple's storytelling is really good. They are doing a good job on taking leadership on a limited set of privacy issues that you can convince busy people to feel strongly about. Whether or not that objectively matters is an open question.
End-to-end encryption is certainly the most relevant feature for these scenarios.
App store DRM is a red herring, as a developer I can still run as much untrusted code on my MBP as I want and I don't see that going away any time soon.