The short explanation
A supply rated 5V 2A can deliver up to two amps. A standard single USB port is specified at 5V 0.5A — a quarter of that. The connector is identical either way.
Where you run into it
Underpowering an HDMI device produces confusing symptoms rather than an obvious failure: it works at low bandwidth and drops out at high, or the display flickers only during demanding scenes. It reads like a cable fault.
There is a useful nuance. USB ports are often implemented behind a four-port hub chipset that shares its budget across all four. Use only one of the four and you may be able to draw up to 2A from it, which is why powering a device from a TV or computer sometimes works perfectly and sometimes not at all.
How the DR HDMI 8K handles it
The DR HDMI 8K ships with a 5V 2A supply and that is what the manual recommends. In practice it needs roughly 5V 1.5A to operate at full capability, so a single standard 0.5A USB port is not enough, while one port of a four-port hub with the other ports unused may be. If a chain fails only at the highest bandwidth, power is worth ruling out before the cable.
Want to test your own HDMI chain?
The DR HDMI 8K is sold through the HDFury.eu web shop.