Let's consider fast typing for subsequent keyboard keys. This time, you will type with small fingers and practice only two keys. Small fingers, as I mentioned earlier, are very extensively exploited in the upper row of keyboards. In fact, the index fingers are responsible for clicking the largest number of keys - 8 for keys each finger and for small fingers - 6-8 keys depending on the keyboard side and the keyboard layout.
If you do this part of the keyboard typing course, then you probably learn to type quickly on a physical keyboard. In recent years, however, mobile devices have taken over the world. Physical keyboards would seem to be a thing of the past. However, laptops are still being produced. The iconic iPad Pro from Apple got a physical keyboard with a touchpad, which in the times of Steve Jobs seemed unthinkable.
Typing on the on-screen keyboard is a bit uncomfortable. It's also hard to type without looking at an on-screen keyboard, mainly because screen keyboards are almost never full-size. It is probably for this reason that the physical, full-size iPad keyboard was greeted with great enthusiasm.
On-screen keyboards are unlikely to be replaced by physical ones. People want small devices and the keyboard takes up a lot of space. However, I believe that screen keyboards at least in tablets can evolve so much that clicking on such a keyboard will be more like clicking on a physical keyboard. Then, typing on the on-screen keyboard will become much more comfortable.