You're awesome! Why? You're about to download Default 3D Low!
This very pack would be your way to go, should your computer you're using isn't that powerful.
Considering it's derived from Default 3D High. In comparison, it lacks quite a few block models and features pack-specific block models instead. This ensures the pack will run as smooth as it possibly can.
Models in this pack also features 'smooth edges', this means all edge pixels connect seamlessly with adjacent pixels, creating a pleasing experience.
Download: Default 3D Low