Hey Staudey, thanks for your testing. I kind of remember having compiled this budgie-previews exposé thing on my last install. But it was laggy too and didn't work reliably. Back then I didn't know whether it was a problem with my system (had installed Budgie along GNOME) or with this previews program. Well, guess now I know.
Right now I am using skippy-xd with hotcorner-applet. Works without flickering and glitches if I disable tooltip in skippy-xd config file. This disables display of window name on mouse hover.
How can anyone live without such a overview feature?