CWDenver wrote:
Can I secure my entire Apple Keychain set of passwords with a separate access password like those found in third party password managers (instead of a general biometric or device passcode), on Mac and iOS?
Yes it is called your admin password. Nothing further needs to be done.
If you change your admin password, the keychain password does not change.
macOS - Security - Apple macOS - Security - Apple
Apple Platform Security - Apple Apple Platform Security - Apple Support
Mac app security enhancements
Mac app security enhancements - Apple Support (CA)