Here it says I can't use
snap to grid and
smart guides at the same time:
Note: When Snap To Grid or Pixel Preview is turned on, you cannot use Smart Guides (even if the menu command is selected).
Now if I want to place an object at a different position to any smart guides, how can I assure that it is placed on "even" coordinates. Can I maybe add smart guides for every 80px vertically and horizontally? It bugs me that I have to manually adjust it afterwards all the time e.g. because it placed the object 0.002px too far to the right.