Custom RSS feed with custom url

Yes, it is possible to customize feeds. In your case, what you want to do is disable to normal rss feed and replace it with a template of your own. Like this:

remove_action ('do_feed_rss','do_feed_rss',10,1);

This line is a bit confusing. The first do_feed_rss is the name of the action hook. The second is the default function on that hook. Now you can add a new action:

add_action( 'do_feed_rss', 'wpse305438_custom_rss', 10, 1 );
function wpse305438_custom_rss () {
   load_template( TEMPLATEPATH . '/my-custom-feed.php');
   }

Beware that by default WordPress will relay /rss to /feed. Changing that involves hooking into rewrite_rules_array.