A 14-year-old male with a class I occlusion complicated by mild crowding of the lower incisor teeth

We know that we need to extract second permanent molars. What are it’s disadvantages if we go ahead with this option? Is there an optimum time to extract lower second permanent molars to obtain the best eruptive position for the third molar?

In the same way, if there was crowding in the anterior region of the maxilla. Then, What are the indications for extracting a maxillary second permanent molar?

Link: https://drive.google.com/file/d/1G4n6TZ_EOFozexnRWh08cBvncUZQ1OjS/view?usp=drivesdk