There are no shift kits(real shift kits can achieve very firm shifts) for any of the 5R automatics. All of those VB kits available are correction kits, they are for correcting inherent problems, and improving the shifts. They are all good to use, they do firm up the shifts, and unless something is wrong, they never create harsh shifts.
The term shift kit is abused, TransGo had the rights to those words, they were the first. The rights to "shift kit" ended long long ago, so everyone now uses the words.
Lots of real shift kits are available, but only for the most common performance vehicle transmissions. The AOD Ford and all related trans' can get shift kits, and correction kits too. That means the 4R70W is fortunate to have choices of the correction kits, which run about $40, and shift kits that are typically $100.
With correction kits(not what they call them, go by the price), if there is a choice, select the firmest choice, they will not be too firm. You have to be very careful when selecting firmness for a real shift kit, those do get harsh. Regards,