Very difficult to drag image icons around the desktop in OS X 10.12.6
The ‘preview’ is Quick Look, a feature released in 2007, originally activated through pressing space on the keyboard (not to be confused with preview the app). In addition to space, activating it through Force Touch on the trackpad has been around since the introduction of Force Touch. Not that I'm saying you haven't had this problem before, but the feature isn't new with 10.12.6.

It's possible you've stumbled on a bug with that version of macOS, where the Force Touch sensitivity or drag-detection is failing. You can provide feedback to Apple here:


https://www.apple.com/feedback/macos.html


You can completely disable Force Click in System Preferences → Trackpad → Point &amp; Click by unchecking Force Click and haptic feedback.