Right! Sorry. I don't use Windows. Honestly? My recommendation about password managers probably shouldn't extend to Windows; there might be no password manager I confidently recommend on that platform.
That's not a statement about 1Password; it's about the fact that the security models are different on the two platforms, and I'm very familiar with how 1Password works on macOS and less so on Windows.
At that point you should probably be about as (in)secure as access to the platform is. I don't know how you could improve much on that (assuming secureboot and bitlocker encrypted disk).
Is there some magic going on the MacOS side that somehow improves on this?
Yes! The actual encryption of passwords is not the hard part of a password manager (though, of course, commercial password managers seem plenty capable of screwing that up!)
The hard problem is getting the passwords out of the encrypted store and into form fields in your browser.
Would you consider the KeePassHTTP solution to be adequate (they have a browser plugin that acts as a password manager using the browser's APIs and the passwords are retrieved after authenticating the plugin with the KeePassXC server -- which prompts the user each time and only entries that match the URL are sent).
They also support copying the password to your clipboard (which they then clear after a few seconds). There's also the automated entry system which basically emulates keystrokes.
Apart from 1Password 4, there used to be a lesser known 1Password for Windows Modern Alpha/Beta[1] which was a UWP app and supported local vault. The Windows Modern version is no longer in development as far as I know, but I hope they add local vault support to the 1Password 6 for Windows in the future (even though I'm a happy paying 1Password.com user).
1Password 4 for Windows uses local vaults just fine - I'm using it right now. The new 1Password 6 for Windows does not support local vaults.