Yes. Outdoor External Water Filter are recommended to install one for our home. The benefit is like what you said above. My personal more likely to recommend take 3M AP903 Model which tested and certified by NSF42. There are one seller in this forum here. 
After I did some research on 3M outdoor external filter, I have no doubt about it. As for your indoor choice, you should think twice about it.
Well, not really. Of course the more standard the product certified have, the better the product, but to choose proper qualify good drinking water system must have at least NSF 42 and 53 certified which is the Aesthetic Effects & Health Effects.
Somemore must fully unit verify and certify, so is no just only the components, there are few brand selling in the hypermarket or we often seen, those system is just components certify but not the full unit. Like a car, example: a Certified imported Honda Brand Engine put into a local OEM Brand car.