Fast flowering means that if the bee can pollinate trees, it'll do so faster then it usually would. (Having two different types of trees within the bee's working range may result in some leaf blocks mutating. Using grafters on these blocks increases (guarantees?) sapling drops from them. Yes, you can breed trees like bees, using bees.)
The territory serum increases the working range of the bee (or in your case, sets it to average). Higher range means the bee doesn't need its flower-type item to be so close, nor do trees need to be so close to get pollinated, nor do things need to be so close to benefit (or suffer) from the bee's effect.
Most bee species you come across are only of any use in order to mutate to another species. Given that mutation only happens when a princess dies and produces more offspring, decreasing lifespan as much as possible will lead to faster advancement through the different races. The racial trait isn't the only way to do it, mind you.
While alive, a bee will produce at the same rate regardless of its lifespan. But a dead bee isn't producing resources, so even in an automated setup where your hives are automatically refilled with princesses and drones, longer lived bees will produce slightly more resources (as they spend less time in your piping system and more time in the hives).