mirror data

Why is Windows 10 doing this to disk 2 and not giving it the same size as disk 5?

I've never done this before, and failed to google. From what I understand I can just mirror everything, and replace drives and I am done. Can i use Dual Slots RAID Enclosure? Set it to raid 0, mirror (do i use soft?). And when I stick new drives into my computer, they will be bootable and work...

My laptop's screen is kind of broken (still usable, but not pretty), so I decided to connect it to a monitor. Unfortunately, now it seems that my laptop only uses the integrated Intel HD Graphics card instead of the Nvidia card which is also in the laptop. This becomes a problem when I'm playing...