Yes, the adjustability range is usually about 5# give or take a pound. And, yes, you can adjust the tiller with the turn of a limb bolt. The average joe can certainly do it. Helps to understand tiller, of course.
I agree, if you take the best ILF limbs and put them against a mediocre TD, the ILF limbs will probably do better. But if you put the best TD limbs against them, the difference,if any, would be miniscule. There are a lot of ILF limbs out there that are mediocre as well. They don't stack up very well against the best T/Ds. So the difference is in availability, selection. One can buy high or mediocre performance in either.