It's more important if you also intend to bottle condition the beer as it will leave more yeast ready to do the job of bottle conditioning. The yeast book also says that beers cold crashed (chilled in less than 6 hours) can cause the yeast to express esters. I don't know how evident this really is - maybe the average palate would not detect it.
Yes. I don't know that I've tasted any significant ester difference between primary and secondary when cold crashing either into secondary or straight to keg. You should be fine.
I do like to crash before racking as it makes for clearing in less steps.
In theory dropping the temp slowly allows the yeast to stay active. Though I doubt that it works, it is hard to argue with the quality of german lagers.