GhosSst :
The ASRock z270 killer SLI/AC motherboards dimensions are 12.00x8.8 and I know most ATX MoBos are 12x9.6 so I want to know if this unregulare sized Motherboard would cause and issues (eg. installing it or anything)
it probably won't cause much of an issue. Just be aware that the mounting holes may not fall in place for the ones toward the front of the case. If that happens, carefully support the motherboard as you plug the cables and wires in on that front edge. (RAM too, but that may be better done before mounting the motherboard.)
EDIT: after review of this board (primarily the
Tom's Hardware review, no issues were mentioned about the installation of this motherboard. So, no worries in its install.