To achieve ideal smile and facial esthetics, as well as normalising airways and breathing, the consideration of a small lower jaw naturally has to include a discussion of the upper jaw. Almost all people with a small mandible will also have a small maxilla.
A retruded mandible and a small maxilla is extremely common. An asymmetric mandible also means an asymmetric maxilla. In a global assessment of a face, it's rare a single growth problem doesn't affect another area of the face that would've otherwise been normal.
The single biggest effect of the small lower jaw is that it causes the upper jaw to become a little, or even a lot smaller. In younger teens, a small upper jaw can be corrected with expert orthodontic treatment that allows for the small lower jaw to be corrected with IMDO surgery.
In older teens, the upper jaw may need correction with LeFort surgery. Setting the position and shape of the maxilla is the key aspect in creating the rest of the face around it. Correcting the maxilla first allows for planning of the ideal dimensions of the mandible.