https://f30.bimmerpost.com/forums/sh...24&postcount=4
for reference, in the link above, thisismikeyb has a lowered F30 with 245/45/18(26.7"), which has same 3-D girth as 245/40/19(26.7"). of your choices, this width and diameter has the greatest potential for rub while turning full lock, especially with contamination build up on the tires. from what hes posted, he's never had problems, even in winter.
im sticking with my original recommendation of 255/35/19 for best performance during non winter conditions and arguably best appearance, especially when lowered.
235/40/19 if in wintery conditions more often than not.
fyi, KW V1 min lowering (highest height) is close to as low as you'd want for xdrive front half shaft (axle) angles. some with xdrives have gone real low but why risk it?