we want to change for password sync to pass trough authentication? When I set up pta what is with the existing accounts? Will the change to pta? Will the password remove from the azure ad when the user sync (ad connect) with pta?
To switch the auth method, simply use the AAD Connect wizard and select the corresponding option. Existing users will be converted to using PTA, unless they are cloud-created users. Passwords will not be affected by this, however from now on authentication will happen against the on-premises AD.