What are the verifiable privacy features macOS provides?
Apple has detailed pages describing their intent and operation. There's also an overview of the security technologies used in MacOS.

On MacOS, the main feature is FileVault (or the default encryption on the newest Macs with "T2" controller chips. Disk encryption means that the data on your Mac can only be accessed by someone with the password.
Safari has been at the fore-front of technologies to stop user tracking and maintain privacy.

On iOS, I'm sure you will have seen new reports of the US government wanting Apple to help them get into iPhones, and Apple indicating that is unable to comply, (and also unwilling). Here's Apple's iOS Security documentation.

There will always be vulnerabilities, exploits, and mistakes, of course.