Best of the best was the Selectric II - the best production typewriter ever. I got typing speeds in excess of 145 words per minute on one of those things with good accuracy. Mind you, copy typing legal briefs was an excellent way to train up my fingers. The actual keys were lovely - had a dip in the middle that really helped you not miss-hit it. No such thing as autocorrect, so fixing a mistake took a lot longer than getting it right the first time. Modern computer keyboards are nothing like as user friendly, so all the magic auto correct aids are needed to produce readable text. Actual speed I reckon is about the same as a modern computer keyboard. It’s finger dependent and brain dependent not mechanics dependent.