I could not quite figure out how the mechanics behind this work. They will start out firing the same patterns at first, but they will then start firing different patterns.
The two dolls are also an important factor. The total number of Point Items collected throughout the game is being counted next to the blue 累計 text.
The item count in the current stage is displayed on the right side of the screen next to the 点 symbol. The goal is to reach Dream Bonus Max as soon as possible, so that more items will be collected at 200,000 points. This is displayed as "二〇〇〇〇〇" in Japanese. In addition to this, the maximum value is increased to 200,000 when playing on Lunatic. Once the Dream Gauge is maxed out, every item collected will give it's maximum value, regardless of where on the screen you picked up the item. Every time the Dream Gauge changes color, the invisible line where the collected items will give 51,200 points goes down, meaning you can pick up these items gradually lower to gain 51,200 points from them. Collecting an item at this value will increase the Dream Gauge by a large amount. In this case it would show up as "五一二〇〇". The text would display in white if the value was not maxed. Collecting Point Items at the highest value (51,200) can be observed from the item value being displayed in yellow text.