My primary is also a N5 but how do you highly optimize pure android? It's as optimized as it can get right out of the box.
There's a lot one can do, but it takes a full understanding of the Android OS to optimize it to each users workflow. How and when apps update, sync, and by switching to the ART environment. While it's still very new and not finished, there's the opportunity to use different libraries. It's not something a regular user would attempt but it's a developers dream.