Question About Best Secure/Private Smartphones

No not really.
One of the few methods is possible to use.

  1. USB Debugging to uninstall the google services in general, then completely disable developer options after the fact.
    Do be warned: Do Not uninstall critical apps or ones that look critical to this device using the method, and for security reasons, Have it off when you’re done, period. More importantly if that device gets factory reset, they do reinstall.
  2. Disable them, This doesn’t require ADB or USB Debugging and should have similar functionality and remains security in tact like above but when you disable it after the fact and should be safer.

USB Debugging does reduce security yes, but since you’re using it temporarily and you’re turning it off after the fact, it is fine (and not just USB Debugging, also developer options should be off after the fact)
and you should once you know you’re done