Great plugin that gets the job done with no insecure errors.
I found that also changing my sites urls to https in general setting works the best. Especially using Yoast SEO to default my sitemaps to https. Otherwise sitemaps are http and force https does not work.
I also use this code snippet in wp-config to force wp-admin to https:
define('FORCE_SSL_ADMIN', true);
if ($_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https')
$_SERVER['HTTPS']='on';