When unchecking VERP option I am getting an error "Boolean value required for track_civimail_replies"
Not similar, but related issue is already logged on gitlab issue. enter link description here and has been fixed and will be available on 5.37 release.
You can either wait for 5.37 release or apply patch.
Alternatively you can add below line in civicrm.settings.php to turn off VERP setting.
global $civicrm_setting;
$civicrm_setting['Mailing Preferences']['track_civimail_replies'] = FALSE;