While the design of the side panels gives you an angled surface at the center, the entire side is actually made of glass or metal with holes drilled through the material to secure the portion which are lined with the leather. That is an interesting approach as we rarely see glass with penetrations in it and the Heritage Pro has a total of eight, two of which are actually for the hook that hold the strap.
The interior of the Heritage Pro has been arranged to minimize height. This is achieved by the PSU in the front, with the motherboard tray otherwise being in a pretty traditional location. The case has all the cutouts to allow for BTF motherboards as well.
As there is no fan mounting room in the front, you get the placement on the floor and in the ceiling. The IO PCB is completely visible when the chassis is apart, but will be mostly blocked from view with your power supply. That said, it would have been really helpful for the floor of the chassis to have a few hooks for zip ties.
The PSU bracket means that the interior connectors of the unit will be facing down. At the highest position, there is still plenty of room for an AIO or fans, but the fact that you have your power supply here means that you have to watch the length of your GPU in the most extreme scenarios. Montech mentions 400 mm in clearance, but that seems like a best case scenario with an ultra-short ATX or compact SFX unit. On the side of the case you will find a mounting position for two additional 120 mm fans. Airflow will be mostly limited to the bottom of the two, as the side panel gets in the way of the one in the top.
In the rear, the five expansion slots have the screw located on the exterior of the case to give you as much room as possible. A nice hinged cover with a thumb screw is present, so that you don't have an unsightly opening in the rear of the Heritage Pro. Above that, there is that 120 mm exhaust fan. Montech has done well by including PWM based fans which are understated and lack ARGB, which feel like a good pairing with the case overall.
Looking at the two side mounting fans from the other side, you can see that you are meant to secure the fans on this side using the included long pin screws. This means that these units are going to be quite close to the exterior side panel, which further underlines the fact that the top fan will lack access to draw air into the case. To make matters worse, the PSU will further limit the effectiveness of these. Instead, Montech could have used this area to allow for more storage for example. The Heritage Pro only has room for two on the embedded mounting plate with the ability to only have a single 3.5" drive or two 2.5" units.
All the cables within the Montech Heritage Pro are sleeved black and both USB variants use flat-band cables. That is beneficial for ATX boards, but those with BTF connectors may even prefer the rounded ones instead as the bend goes down when cable managing, instead of sideways. The power cord is angled 90° and deliberately flat, so that it will not interfere with any ceiling cooling. Lastly, there is the unified front panel connector to make this step of the assembly process as easy as possible.