"Hardwired to door switches" means that it monitors the door pin wires and will go off if a door is opened. Just about every alarm of its type uses that kind of input. It's saying it doesn't just rely on wire voltage monitoring like an all-in-one, "two-wire" alarm.
Dome light supervision is something different altogether. If you hook up dome light supervision, it means the dome light will come on when you disarm the alarm so that you can see into the vehicle before you open the door.
In many vehicles, the door pin switch wires are connected directly to the dome light so you can hook the trigger input up to the dome light wire. In other vehicles, there are separate door zones for the lighting or delayed turn-off dome lights, so you might have to find the actual pin wire or use diodes to isolate and connect different pin wires.
For this type of alarm, one isn't all that much more difficult to install than any other. The difficulty level of the installation will be determined by the vehicle.