This example shows how to identify the different system groups provided from EE_event->question_groups()

example.php

<?php   
/** @type EE_Event $event */
$event = EEM_Event::instance()->get_one_by_ID( 1 );
$question_groups = $event->question_groups();
foreach ( $question_groups as $question_group ) {
    if ( $question_group instanceof EE_Question_Group ) {
        switch( $question_group->system_group() ) {
            
            case EEM_Question_Group::system_personal :
                // personal question group
                break;
            
            case EEM_Question_Group::system_address :
                // address question group
                break;
            
        }
    }
}