How to tweak or turn off 3D Touch on the iPhone 6S
But 3D Touch isn't for everyone. Some people aren't a fan of the way their iPhone "buzzes" in response to their touch - that's Apple's Taptic Engine at work, giving you brief moments of feedback to let you know you initiated a 3D Touch action.
If you aren't a fan of 3D Touch, or simply want to adjust the effect, here's what to do:
Go to General > Accessibility > 3D Touch.
From the top of this menu, you can turn 3D Touch off with a simple toggle, and you can adjust the sensitivity of 3D Touch so it registers with lighter presses.
Personally, I chose to change my 3D Touch sensitivity from "medium" to "light," so you don't have to press so hard into the screen to start 3D Touch.
You can test out the 3D Touch sensitivity right from this menu as well. Apple provides an image you can 3D Touch so you don't have to keep going back to your settings.