The perception of speed in using a computer is almost entirely latency driven these days. Compare using `rg` or `git` vs loading up your banking website.
Linux desktop (and the kernel) felt awful for such a long time because everyone was optimizing for server and workstation workloads. Its the reason CachyOS (and before that Linux Zen and.. Licorix?) are a thing.
For good UX, you heavily prioritize latency over throughput. No one cares if copying a file stalls for a moment or takes 2 seconds longer if that ensures no hitches in alt tabbing, scrolling or mouse movement.
Exactly.
Exactly, lots of different things.
When I alt-tab I care about latency.
When I ssh I care about latency.
When I download a 25GB game I care about throughput for the download to a certain extent that is probably mainly ISP bound rather than local system bound. I don't care if the download takes 10 or 11 minutes as long as I can still use my system with zero delays meanwhile. And whether it takes 11 minutes of 3 hours depends on my ISP mostly. But being responsive to me while it downloads is local latency bound.
The Youtube example you have makes sense, sure.
In the example you gave the amount of read speed the user needs to keep up with a video is meager and greater read speed is meaningless beyond maintaining a small buffer.
You in fact notice more if your process is sometimes starved of CPU IO memory was waiting on swap etc. Conversely you would in most cases not notice near so much if the entire thing got slower even much slower if it's meager resources were quickly available to the thing you are doing right now.