Good morning.

I have a 3-axis CNC with MACH3, when I need to cut adhesive sponges or films I use a V cutter
https://aliexpress.com/item/4000748313545.html

I have seen that exist plotter nibs, which can be used without rotating the motor.
https://aliexpress.com/item/1005001773642793.html

I don't understand if they have an internal bearing, the motor is free to rotate but has inertia.

From the picture it looks like it is off-centre, so it needs a correction in the GCODE programme, either a conversion from another GCODE or a GCODE generation for nibs or a programme/plughin that moves the machine in the correct way.
In all cases it must lower Z to cut.

Do you have any advice for me?

The method of a free rotating spindle is commonly referred to as "drag-knife". The nibs shown in the link are likely used in cnc film cutters like Roland that actively orient the blade to the direction of the cut.

I'd check the Mach3 forums or CNCzone for guidance.

Cannot inkscape generate that kind of Gcode or correct the path to compensate for the stylus?