Are you able to take a video where you capture your typing speed vs the keyboard input speed? Would be interesting to see the discrepancy, as I doubt a human would be able to type faster than a keyboard would be able to input characters.
But let is know how the factory reset goes. If it's still slow, is return it for another.
Fun fact for people who don't know (you probably do know). The reason for the design of the QWERTY keyboard is to slow down typing back in the old days when manual typewriters were used. People were indeed able to type faster than the typewriter keys could function, and the typewriters would jam. The layout was supposed to make people type slower than they would otherwise.
I did learn to type on an old fashioned typewriter, and I can remember keys getting stuck together, because I still typed faster than what the typewriter could do even using a QWERTY keyboard.
Even though desktop PC keyboards aren't going to jam up from fast typing, I'm not as good at typing as I was back in high school. I wouldn't be able to cause an old fashioned typewriter to jam up nowadays if I discovered one at an antique store.