they do mail order, sure, but a lot of people prefer to pick up their capsules at the boutiques because they don't have to pay shipping like if they order it by mail. most people seem to think it's worth it... but like i said, this leads to serious overcrowding in the stores during peak times and it can make wait times pretty bad... last time i bought a descaling kit in zürich on a saturday i had to wait in line for 20 minutes just to pay for it.
i go to my local boutique on weekdays before 4:00. the store is usually almost totally empty then.
a nespresso machine will make either short or long coffees, they have capsules that are specially designated for short (espresso) but they actually can be used to make a long coffee if you want. they also have special capsules for long coffee (lungo)... i wouldn't use those to make espresso though...
they do sell flavoured or special edition capsules at certain points during the year but it's not something that is in their regular line-up of coffee, no.
there are also certain machines that have an integrated milk canister so you can make cappuccino, latte macchiato, etc.