I have a rarely used Wacom tablet, it does what it says when it comes to drawing and sketching (it fails to improve my limited artistic abilities though). Pens and touchscreen aren't the same thing. Daubing away with a finger is different, pens offer precision abilities.
Like with most human interface devices, you get what you pay for, cheap is cheap, you might get away with basic annotation on a cheap device, but once you want to sketch something, nah, stuff like pressure and tilt sensitivity are necessary. The iPad pencil approach is very good, but then, not cheap either.
As said, like with any human interface device, you need to try them and find something you're comfortable with. But good solutions come at a cost.