Plex is a media server first and a live TV client second, which is why plugging an IPTV line into it works for some people and frustrates others. The difference is mostly about what you expect it to do.
What Plex was designed around
Plex’s live TV support was built for a tuner and an antenna: a fixed set of local channels, a guide supplied with them, and recording on top. An IPTV line is a different shape – hundreds of channels, a guide from a separate source, and no tuner hardware anywhere. Getting the two to meet takes configuration, and the result is often slower to browse than a purpose-built player.
Where it works well
If your goals are modest, it can be a good fit.
A small, curated channel list rather than everything on offer
One household interface for films, series and a few live channels
Playback on devices where Plex is already installed
A setup you configure once and rarely change
A guide you are willing to point at manually
Where a dedicated player wins
For large channel lists, fast zapping, catch-up and a guide that arrives with the line, an ordinary IPTV player is simply better suited. Most of them accept a server address with a username and password, or a playlist URL, and they are free.
Either way, the line is the same
Whichever route you choose, what you are buying is unchanged: credentials that a player points at. Test them in the app you intend to use before committing to a long plan.
A line for whichever app you prefer
Plex, a standard IPTV player, or both. Free trial first, then a one-time payment with no auto-renew.