When doing character design, you should be considering the polygon counts, how many polygons is needed do make the character look good. If it's a player character or NPC the polygons vary, NPC usually have low poly considering the player won't interact with them. High poly can be an issue which could slower things down.

Platforms can be different considering if it's a mobile or console due to the screen sizes. Mobiles have a smaller screen size with have lower polygons. In LOD (level of details) it's important to think about the distance of the character, therefore it's good to create several versions of the same character with different poly counts. Having a high poly when the character is far away will only slow things down.

For the brief the goal is to have a low poly which is around 1500-15000 polygons. The importance for the material properties it to avoid any loose clothing, shoulder pad, metal, it could cause some issues. There will be a walk, run breathe, combat, idle animation that should be suitable for the character, it's not about the physical appearance. Any areas that bends is called deform, the deformed areas should have more edge loops. Otherwise it will become an issue when bending the elbow as example. There should also be close fitting clothing for this brief to avoid any issues when animating, both skin and clothes should be a seamless mesh,