If you wanna know about it, you should watch in youtube about making crash bandicoot. They were trying to make the gameplay as efficient as possible and making sure that user experience is not affected by it. For example, you only need to load data per level, in case big data needs to be loaded once per level, they will load it from the disc.
Another big problem they have to solve is how to make the crash character fits into the system with too many "models"
Another big problem they have to solve is how to make the crash character fits into the system with too many "models"