A:AnswerNot sure if you're asking just about the case or how it's represented in the images, but this isn't a whole computer. It's just a case. However, I'll answer just on the case itself. The H5 was a very popular case when it came out, most NZXT cases are. However, a lot of NZXT cases had glass fronts, meaning very little ventilation for air intake, which would hamper overall cooling. The H5 flow fixes this by utilizing a metal mesh front panel with plenty of airflow, allowing for much better cooling. That, combined with plenty of other vents, mounts for various fans or radiators (AIO or custom built), means this will be a good case from a cooling standpoint.
A:AnswerYou technically could depending on your wiring skills. Get an 18" sata cable and a power supply extension and mount the drive externally. I have this setup for both my H5 flow cases.
A:AnswerIt does not come with a motherboard, you must purchase a motherboard too. You can fit an ATX or a Micro ATX board.
Look for companies like ASRock, Gigabyte, MSI, or ASUS if you need a reliable board. MAKE sure to check that all your parts are compatible on PCPartPicker, it will tell you if any parts on your PC build may conflict!
hope this helps!