One of most important features of all video game 3D models is the Poly count. Low poly models must be optimized for low memory usage.
This is not a triviality, that’s why when you work in a 3D model for video game implementation every single poly count. This optimitzation should be take into acount from the very beginning with the character design.
Quads vs Triangles:
Why is better to use Quads instead of triangles? Because Quads work better whith Subdivision Surface modifers. This allows you to deform the mesh without breaking it down wich is extremily important when you want to rig an animate a 3D model.
Otherwise, we can not forget that 2 triangles are equivalent to a Quad and for most computer graphic systems work only with triangles.
No matter if you use more or less triangle or quads. The main goal in low Poly modelling is to get a clean and harmonius mesh.