There a few different sizes (also known as ‘form factors’) of motherboard commonly available, so most cases have screw positions that will accommodate the various sizes of motherboard.
There a few different sizes (also known as ‘form factors’) of motherboard commonly available, so most cases have screw positions that will accommodate the various sizes of motherboard.  You don’t need to install mounting standoffs in all of them; just the ones that match your motherboard will be fine.