On my iPhone/iPad I use
Cloud Stream IPTV Player which is also compatible with Apple TV (although I have not tested the latter).
It can import local/cloud m3u files and is one of the few players to be capable of rtsp streams (local cable TV via router).
It's designed very clearly/simply but offers buffer size and deinterlace options.
It's free. But you can purchase/unlock some optional features or tip the developer - I did.