I've noticed for fans when it comes to this case that it's said that it has 120 mm spaced slots. Does this mean I have to buy a power supply with a fan that is 120mm? If not, is that irrelevant and only for if I want to add additional fans? Is it the dimensions of the case and power supply that I have to worry about? Either way, thank you very much to anyone who can help out.
It looks like you've picked both an atx standard mid tower case and a stand atx power
supply so you shouldn't have any problems with fit. The 120mm fan in the PSU is just its
cooling fan and when you install the psu into that case the psu fan will draw cool air in
through the vent below it in the bottom of your case and exhaust warm air out the back.
The references to 120mm fan mounts in that case are both to the one 120mm fan that
comes pre-installed at the upper rear of the case and other spots in the case where
you can install additional 120mm intake and/or exhaust fans should you so desire.
I noticed that you can also add a 140mm fan at the top of the case to exhaust hot air.