There are several different Samsung S Pens. I am referring to the S Pens that come with the Samsung Galaxy Tab series.
RATING: GOOD. The S Pen uses standard Wacom EMR and delivers a consistent drawing experience to what you would find in drawing tablets. I prefer it to the Apple pencil though it is not as good as the Wacom Pro Pen 2 in terms of pressure range.
The overall pressure of the S pen is good.
maximum pressure
In my testing it has a good maximum pressure of about 250gf.
Initial activation force
It's supposed to be around 3gf.
I have not independently verified this.
The S Pen has one physical button, unlike the Apple iPad. This also differs from the pens of most drawing tablets like the Wacom Intuos or Wacom Intuos Pro. Those pens have two buttons, and some have three.
I have 3 Samsung S pens. They are all the same model but different colors. They came with my purchases of the S6 Lite (2022 edition), S8 Ultra, S9 FE.
They use the same Wacom EMR tech. In fact they are cross compatible, you can take the Wacom One GEN1 Pen (CP-913) and use them instead of the S Pen with the Galaxy Tab S series tablets. And the reverse is true, I can use Samsung S Pen with the Wacom One tablets.
And just like those Wacom pens they don't need to charge - they get their energy from being near the tablet.
There are several versions of the S Pen listed here: https://en.wikipedia.org/wiki/S_Pen
I can't speak to all of them, just the ones that came with Galaxy Tab S series.