Streaming services love to throw round numbers at you, "you'll need 25 Mbps for 4K" and so on, but the truth is messier. The plan on the bill is rarely the speed reaching the TV, and the TV itself often can't pull what the line is offering. Before you upgrade your package, it's worth knowing what each service actually asks for and where the bottleneck usually hides.
The numbers above are per stream. A typical evening in a family of four, two 4K TVs running, a kid on YouTube, somebody on a Zoom call, easily asks for 75 Mbps of clean headroom. Most "Netflix keeps buffering" complaints we hear aren't a bad ISP at all; they're a 50 Mbps plan trying to do the work of 100.
Pre-recorded content is buffered, so jitter is invisible. Live sports, news, and Twitch are not buffered as deeply. High jitter causes stuttering and dropped frames. Aim for jitter under 30 ms for live content.
Almost always the WiFi link, not the ISP. A smart TV with a 2x2 802.11n adapter can only do 50-60 Mbps over WiFi in real conditions, and that drops further if it's two rooms away from the router. Plug it into Ethernet or move the router closer.