In my new 2018 MacBook Pro with High Sierra a very annoying preview pops up if I press and hold the touchpad down on an icon on the desktop.
This makes it very difficult to drag stuff from the desktop to somewhere else. And I use that a lot by taking screen caps to desktop and then dragging them to where ever I need them.
I want to disable this feature for good.
I believe you are talking about "3D Touch", a.k.a. "Force Touch":
https://en.wikipedia.org/wiki/Force_Touch
I don't have one of the newer macs with this feature, so I don't have direct experience.
Basically it distinguishes between a normal touch and a stronger "Force Touch".
I have been told that all it takes is a bit of personal "training". If one gets used to not put as much pressure on a "normal" touch, people tell me, it quickly becomes easy to not engage force touch by accident.
The article below tells about disabling this feature. But it may be worth to try and use it. I find the analogous quite easy on the iPhone, and never engage it accidentally. Just saying.
Just to add, if you don't want to disable all Force Touch features you may find enabling "dragging" in System Preferences > Accessibility > Mouse & Trackpad useful.
macOS Sierra: Mouse & Trackpad pane of Accessibility System Preferences
Disabling touchpad long press preview in Finder
