Premium IPTV players offer features like catch-up TV, cloud recording, and multi-screen view. Free credentials generally lock you out of these features. You get the bare bones—often without an EPG (TV guide), so you have to guess what channel is what.
If you are looking for existing "hot" players that use these login methods, consider these: GSE SMART IPTV PRO iptv stream player username and password free hot
Here are a few (free and publicly available) IPTV stream players: Premium IPTV players offer features like catch-up TV,