Apple Pencil pressure sensitivity

The behaviour you describe would suggest that the issue lies with the Apps themselves. As the Pencil performs as expected with Procreate, you have demonstrated that the Pencil itself is functioning normally.

A forced-restart may be helpful in resolving an unexpected software issue; It will certainly do no harm:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

In Notabilty, when you are using the pen/marker tools, tap on the appropriate pen/marker too, make sure you pick the variable line width instead on the uniform line width option, IF you are looking to get light to dark/thin to thick line.

These option look like short horizontal “squiggly” “S” lines.

One option looks of uniform line thickness, the other looks light variable line thickness.

Best of Luck to You!