do the top buds represent the whole plant-partial harvest?

If the lower buds do not have as many amber trichs can I leave them for a few more days after taking the top buds?

absolutely.... The harvest won't be as good as the top colas, but it will allow them to receive light and further develop. Most people don't do this because they have new plants already ready to begin flowering and need the space, or they are going to convert grow room into a veg room again, with 16-24 hours of light. If you have space and time, I would do that.