Also "Allow Flipping" must be enabled in nvidia-settings.

I also saw a non-synched animation.
The maximize animation happened then the window maximized, so for a split second, there were two windows (one was just a post animation border frame). That could be a side effect of the slow performance and x11 in general.

(In reply to Maxim from comment #0)
> https://bugzilla.gnome.org/show_bug.cgi?id=766685
> These new animations do not look smooth with NVIDIA driver.
> 
> Also fulscreen animations that were smooth before that, they also lost their
> smoothness.

NVIDIA is really only for playing computer games. If you want to play computers games, don't bother with anything else. Otherwise, stick to intel onboard graphics and don't use bother with NVIDIA.

In the meantime, I hacked the animations out (this is likely the wrong approach) in my local build. This works apart from the gtk frame sync issue on CSD windows which the animations where semi covering.

--- a/js/ui/windowManager.js
+++ b/js/ui/windowManager.js
@@ -1312,10 +1312,6 @@ const WindowManager = new Lang.Class({
             shellwm.completed_size_change(actor);
             return;
         }
-
-        if (oldFrameRect.width > 0 && oldFrameRect.height > 0)
-            this._prepareAnimationInfo(shellwm, actor, oldFrameRect, whichChange);
-        else
             shellwm.completed_size_change(actor);
     },