Question how boards fit into cases

[need2sleep]

I have several non-functional computers and hoped to find a case among them that my ATX motherboard would fit into. But I invariably found that the cut out for the I/O panel did not match where the panel was on the board. This makes me think that different ATX boards must have their I/O panel located on different sides (long side, short side), or different locations on any particular side. Is this correct? Do I need to worry about where my I/O panel is on my motherboard when considering a case?

I've been listening to YouTube video reviews of cases identified by PC Parts Picker for my motherboard, but none of them discuss where the I/O panel cutout is compared to where the ATX board might have them positioned. This leads me to the contradictory conclusion that the I/O panel for ATX boards is in a standardized location.

Please resolve the apparent contradiction I'm facing.
Thanks,

 

[13thmonkey]

ATX, mATX, ITX, E-ATX should all be the same in the top left corner and extend down and right (more PCI-E and more memory).
BTX might be different, some system manufacturers have custom boards, or used to (with custom 24pin layouts), with older systems it might be more common.
https://en.wikipedia.org/wiki/ATX
https://en.wikipedia.org/wiki/BTX_(form_factor)