Gigabyte Aorus AC300W ATX Mid-Tower review - Product gallery

Once we look at the right side (or rear) of the motherboard tray (behind the motherboard) we see there is decent space for cable routing, not heaps though. We do miss some rubberized grommet holes but the holes present can be used well to guide all wiring properly. 

To the left and right you can see a three fold of SSD mounts.  These are simple screw based plates, but hey there's nothing wrong with that. 

Here you can a good 2cm of spacing for cables (depending if you route bypassing the shielding). It's a bit limited really as the right side panel does not have some indentation for a bit more cables. So it gets cramped up there quite easily.

It also is difficult to tuck away residual wires and thus pretty much everything ends up just in front of the PSU as there is no other room/space available.

There is one HDD bay with two trays available. You simply slide it in and secure it with screws and the  slide it in and secure the tray with a thumb screws like shown below.