The LCD is connected to the SuperIO chip, specs for which are available online. It is using the Hitachi LCD protocol. Pretty straight forward. The SuperIO chip also runs the cooling fan under purely OS software control. That is, the bios does absolutely nothing to control the CPU and drive temperatures. The fan just runs at max speed until an OS driver takes over. The fan is connected to the SuperIO SysFan control pin. There are several more fan outputs on the SuperIO that are not used. Ideally, software should monitor both the CPU temp and the drive temps via SMART cmds and control the fan speed appropriately.
The VGA output is pretty murky looking, but infinitely more serviceable than trying to install an OS the WD way.
There are PS/2 mouse and keyboard ports on the SuperIO and I have hooked them up, but it stretched my rework/soldering skills way past being worth it. If you hook up the two extra USB2 ports, you can connect the mouse and keyboard there. It’s way easier than trying to get the PS/2 ports working. Otherwise you’re always fighting with not having enough ports for USB stick, USB mouse and USB keyboard. Not as critical for a Linux install, but really frustrating for any GUI install.
As for software vs hardware RAID, the distinction is a bit subtle. It mostly has to do with what else besides reading/writing the individual RAID drives, the CPU is doing. If you setup the DX4000 with no additional loads beyond the RAID itself, I would argue that IS a hardware RAID. It’s when you start loading down the CPU with a bunch of other stuff (ie Plex server, transcoding, torrent client, etc, etc) that it devolves into what I would call software RAID and the RAID performance suffers. The DX4000 box with nothing more to do than manage the RAID, can nearly saturate a Gigabit Ethernet link. Can’t expect more than that.