MPTCP (Multipath TCP) can use multiple network paths simultaneously. Subflow selection chooses which path to use for which packets. Some resellers support smart subflow selection. Very few do.
Here's the subflow selection feature. A British IPTV reseller supporting MPTCP can select the best path for each packet (lowest latency, highest bandwidth). Your stream uses WiFi and cellular optimally.
What actually works for optimal performance is smart subflow selection. Your device chooses the best network for each packet automatically.
I have both WiFi (low latency) and cellular (high bandwidth). My British IPTV reseller's MPTCP implementation sends latency-sensitive packets over WiFi, bulk data over cellular. Perfect optimization.
The pattern that keeps showing up is that IPTV reseller UK operators with MPTCP are extremely rare. It's a cutting-edge feature.
Honestly, MPTCP is overkill for most. A IPTV reseller UK with it is technically advanced but you likely don't need it.
That said, MPTCP requires device and router support. Not widely available.
In most cases, British IPTV MPTCP is experimental. Stick with single-path TCP.