Objects for games can have different mesh solutions.
The game engine, can than switch to low - high resolutions in case of need.
Blender has a module called multi resolution. Working on an object in different resolutions.
The holes are the main resolution issue. But when a ball is rolling fast over a bowling lane, motion blur. Then do you need a high resolution ball with hole? Or is a versionwith no holes, and a normal map enough (which gives the illusion of holes).
Normal maps and multiresolution, will be part of this course.
If you have enough CPU power, then no problem. In complex games, every vertex counts.