My optical bay is 5¼, pretty standard. My hdd is 3.5, ssd is 2.5 8mm, again, pretty standard. I wanted both gone from the bottom hdd cage as it interfered with how I was reinstalling the 280mm aio and pull fans. So, I massacred an old IDE CD drive, I wanted just the lid. It's the correct size for the bay and already has mounting holes. Painted it black. Drilled 4 holes in the bottom to line up with the 4x hdd mount holes. So, now the hdd sits perfectly inside the optical bay and my ssd is stuck into a factory mount on the backside of the mobo tray. Prolly would have been easier just to buy a 5¼-3.5 drive adapter, but I like to repurpose old stuff. My gpu support is the slide rule from an old circular saw that I heated up, bent straight, sanded, painted and added a little shrink-wrap to the tip. Bolts to the back of the case. Much more solid than the junk that came with the gpu.
A case is just a box for holding pc components. What you do with it is limited only to your imagination and ability. Want a full size window instead of the miniature version stock? No worries, just cut one out and add some acrylic. Riveted hdd cage? Nothing a drill won't cure, it's just a container, add one anywhere. Be surprised just how many ppl velcro the SSD to the top of the psu camouflage in some cases. Ultimate project? Full custom loop as part of a desk, no case needed.