I've been researching this for a bit. It seems using an M3U with the IPTV Simple Client is unable to assign any sort of pre buffer to the streams. It just tries to play them instantly, and if your stream isn't really robust, it will result in constant buffering because it has nothing to fall back on. This is why there is no play/pause button in the player watching streams, because its just playing straight up whatever the server is giving it. Unlike many standalone apps that handle IPTV & let's users assign buffer to handle this problem, Kodi/LE doesn't for whatever reason. At least not apparently.
Is there ANY way to accomplish or work around this? From my understanding, messing with the advancedsettings.xml is disregarded when it comes to M3U streams. But even a 3 or 4 second pre buffer would make a world of difference. Thanks!