Removing the side panels and taking a first look inside the Antec P20C, there is a clear trend that Antec is setting if you consider some of the details. On one hand, the body of the case and its layout is pretty traditional as there is no need to re-invent the wheel here. But, all the cable routing holes are covered in grommets - including the ones on the shroud, a positively unusual sight. On that shroud you may also install up to two 120 mm fans for additional cooling. Then there is a metal GPU support bracket with a rubber cap on it, which again is actually quite useful for those employing long and heavy cards.
On the other side of the motherboard tray, you can clearly see a large cutout around where the CPU socket will be. Antec has done an excellent job in providing lots of hooks for zip ties and cable management - including around that large, central opening. On top of that, there is a little cap at the top with well shaped cable routing possibilities, giving you just that extra bit of space when routing wires past the top of the motherboard and any installed cooling elements in the ceiling of the P20C.
The two SSD placements under the CPU backplate cutout come with rubber rings and Antec employs metal pins to hold the drives in place. This is a great way to install them and it is good to see Antec continuing to utilize this setup. Towards the front, there are two Antec branded Velcro strips holding the bulk of the cables in place. Unlike the DP503, the P20C does not come with an ARGB controller as it has no need for such a PCB, which would otherwise be installed in the top left corner of the motherboard tray.
In the front, on the bottom, there is that aforementioned hard drive cage. It can hold up to two 2.5" or 3.5" drives, but only one utilizes a pull out tray. If you want to install that second unit, you will have to unscrew the whole contraption, so that you may use screws and tools to affix a drive on the top of the cage. Above that are the three 120 mm intake fans, with plenty of room so that you may install a 360 mm radiator here as well.
In the rear, there are foam pads for the PSU to slide unto, with plenty of space for high-capacity variants that can be longer than usual, so you may fill your system up and not worry about the power delivery aspect. Above that, the seven expansion slot covers are actually held in place by classic screws instead of thumbscrews - another small way for Antec to walk that fine line between functionality and affordability. In the very top, the fan mounting position has elongated holes in order to adjust its placement height to best suit your needs.
Looking at the ceiling, there is lots of space between the motherboard and any installed cooling. Classic AIO setups with a layer of fans should not interfere with your access to any connectors. While sandwich configurations should clear the board easily, you will have to plan your steps to have all the wires and connections in place first - but that is to be expected.
All the wiring within the Antec P20C is sleeved black. Both the USB 3.0 and audio leads are flat for easier cable routing, while the USB-C wire is of the classic round type.