The high amp charger upgrade is an AC charger that allows you to run at 72A if your AC charger/connector is capable of that supply.
This AC charger has no bearing on your Supercharging however as Supercharging is DC which is directly stuffed into the battery pack at some seriously high rates of speed. It bypasses the AC charger(s) though so it doesn't matter what AC charger you have your Supercharging speeds will be the same no matter what.
You will see higher speeds though if you find a destination charger or if you have a HPWC at home connected to a 90-100A circuit. Often times, for cost savings, people will install HPWC's on a 50A circuit which will allow for sustained charge rates of 40A for safety. In these instances your car wouldn't be able to charge much faster than a standard AC charger would allow.
On the rare occasion that you're traveling off of the beaten path, in a hurry, very low on juice and you find a destination charger or friend's HPWC that is on a 100A breaker though you'll see charge speeds approaching 55-60mph which is nearly double what a standard AC charger equipped car is capable of.
It could be used more frequently if you install a HPWC on a 100A breaker at home and regular occurrences where a quick splash of juice to get back down the road would come in handy. For most, a simple 50A outlet provides plenty of juice for 99% of their needs at a much lower cost of install.
You should do some searching as there's lots of details on this topic all over the forum.
