system
A chat on subreddit /r/pcmasterrace
human
USB 3.0 is quite fast especially on read

It is surely faster than old fragmented HDDs

Edit: 24+ GB of ram should allow your system to not read disc multiple times DURING gameplay see RAM page management.
gpt
With usb sticks the problem usually isn't that the interface is slow its also that a lot of the cheaper sticks just have really slow flash or controllers so you would still probably get bottlenecked running some games off an usb