While I really like Winaero Tweaker and some of their other tools (like
Winaero Tweaker and
Get Windows 7 Games for Windows 10) their tweaker does not cover all tweaks as easily as some other tweakers.
So if not too late, you might check out
7+ Taskbar Tweaker. It concentrates on the Windows Taskbar functions, features and behavior. As such, it contains a simple tweak to disable these previews. On the left side under "Hovering", tick the "Nothing" option and that's it - the change takes place immediately.