As you are easily able to remove the sides, top and front panels of the AP201, there's plenty of access for a hassle free build.
The main side of the chassis provides direct access to an upright motherboard in the rear. Towards the front, there is a cosmetic cover plate with branding, which you would only see when opening the chassis. Considering the AP201 doesn't have a window side panel, the cover plate feels redundant, even if it is nice to have. Perhaps Asus considered a variant of the chassis with glass? Behind the cover plate lies the ATX PSU bracket. On the floor of the enclosure, you may install two 2.5/3.5" drives. Alternatively, there are mounting holes for two 120 mm fans.
Turning the case around, you will find the power cable pre-routed behind the motherboard tray. Underneath the large CPU cooler opening, there is a single 2.5" tray. Asus also includes three branded Velcro strips in the cable channel towards the front of the chassis, which should come in handy during the assembly process. The only gripe here is that the top-most placement is not useful at all, and the fact that the Velcro strips should be longer.
In the front, there are three possible PSU placement options, if you have a longer PSU, you may raise it up accordingly. But, even if you have a compact power supply, you will gain access to another 2.5/3.5" slot in the front of the chassis if you mount the power supply high enough. If ASUS would have designed the AP201 to allow for a drive to be mounted in the exterior of the front, with a cable routing hole, then users would have even more choices on how to configure things here. However, to enable that, ASUS would also have to ensure the removable front cover is deep enough to accommodate 3.5" drives for example.
In the rear, the four expansion slots are protected by removable & reusable covers, held in place by classic screws. Above that, the black, branded 120 mm fan is configured to exhaust hot air. You can once again, see the sizable amount of room above the fan/motherboard area for large, ceiling mounted AIO.
Speaking of which, here you may place a radiator assembly of up to 360 mm size without issue.
All the leads within the AP201 are of the default, black variety. The power plug comes angled at 90°, keeping the height of it to a bare minimum, giving you as much flexibility when using ceiling mounted cooling elements as possible.