Dan, thanks for the response and follow-up questions.

Re: responsiveness for Keychain, that might have been fixed in a recent iOS/macOS update as I no longer experience that issue. These days, Keychain just works in every instance. Since it's based into the OS, I don't even think about it being a separate function.

Keychain requires no keystrokes unless you count the tap/click to confirm the username (if there are more than one) or you've not authenticated lately. 1Password typically works the same, but there is a keystroke combination and iOS share-sheet extension for when it doesn't automatically work.

Both use the system authentication and then have another password layer. For example, if a site only has one stored user/password saved, it will auto-populate after logging into/authenticating with macOS. However, switching to an alternative or opening the list of all passwords requires device authentication. iOS requires device authentication every time a password is recalled and added to a login in Safari. 1Password follows this method, where you must authenticate the software to use it the first time during a session on macOS and all the time on iOS.

For simplicity, Keychain wins out. It's baked into the OS and there aren't any settings to tweak, learn, or master.