@Frootism How one recognizes that a motherboard fits in a cabinet or not is based on the key words provided in the cabinet specs.
here the cabinet spec says that it is suitable for an ATX Motherboard and the HAF 912 is an ATX cabinet so you would not have any issues.
The technical term used here is "MOtherboard Form Factor" or simple Form Factor"
The types of motherboard form factors are
Micro ATX and ATX are pretty much common and I doubt you would want to bother about the rest as of now