As far as I know the only way to increase the actual range of archery is to do an .ini edit.

Should apply to both bows and crossbows.
With the maximum range and some time spent working out trajectory, I would guess that you can kill any target at any distance just as long as the target was loaded in and is within the arrows range (set by an .ini value).
Of course, it's not that clear cut, when you take into account some people may use faster arrows mod, which will of course adjust the natural trajectory slightly, and will probably make even longer distance shots possible.