They are proportionately few in the U.S., and probably would be similarly few in this newsgroup. The reason for that is, in most states in the U.S. one must be able to prove (e.g., via certification by a medical doctor) a permanent physical inability to operate a 'conventional' bow in order to 'qualify' to receive a permit to hunt with a crossbow. In many ways it's just another illustration that, too frequently, 'logic' and 'government' are mutually exclusive concepts here.
You have white-tails in Finland?
Considering that both the crossbow and the 'conventional' bow launch a similar projectile at similar velocity, the differences in hunting technique between them are probably few. Unfortunately, I cannot expound from experience because I cannot 'qualify' to hunt with a crossbow, but perhaps my 'theory' and 'speculation' might be helpful.
Probably very similar to that of a 'conventional' bow, perhaps extending to about 50 yards/meters or so.
It probably doesn't matter, as long as the cutting edges are sharp enough. Most archery hunting regulations here specify only that the broadhead must have a minimum cutting diameter of one inch (2.54 cm), and probably all commercially-available brands meet or exceed that specification. I use the Thunderhead brand with my 'conventional' bow, and have found no reason to experiment with other brands.
There seems to be consensus that, regardless the projectile or instrument used to launch it, the 'preferred' shot placement is more-or-less broadside into the heart-lung area, the objective being to deflate both lungs and lacerate the heart and/or major arteries and veins.
-jc-
