how to customize rss feed tags using hooks?

Removing the tag altogether would be inconvenient since it’s hardcoded in feed-rss2.php template file. You could replace the calling function in do_feed_rss2 hook, but still would need to fork whole template.

It is, however, easy to cancel out content there. get_post_comments_feed_link() passes output through the filter, so something like this should do it (not tested):

add_action( 'do_feed_rss2', function() {
    add_filter( 'post_comments_feed_link', '__return_empty_string' );
}, 9);