And why did we use collections instances when making the loop animation? Is it just for organising stuff? Does it make performance better?
The answer is yes. Collection instance allows you to work with all of the duplicate objects as one object. So making adjustments is easier. Collection instances also take less RAM since it only has 1 set of data that is being copied. Also it reduces render times. It only has to apply the material and lighting to the objects once. The only additional calculation is on lighting from instances that have lights that are close to each other and lights not in the instances. There are other optimizations, but honestly I'm not smart enough to understand it.