1. tesla superchargers share a the 'bank of chargers' at 2 spots. look for 2a, 2b, those two spots are shared. pick one that doesn't have a paired spot in use 2. they charger at a higher rate when your car has a lower charge. 3. they cool the battery when charging to prevent harm, if its really hot this can lower charge ability. there's a similar thing with cold temps

They are reliable and predictable with those factors.

There is already extensive discussion of how to charge higher power systems like trucks, tesla has a plan, google for details. the easiest thing is just several superchargers together. by the way, a supercharger spot is just a bank of regular chargers working together, feeding dc directly to your car's battery. its not magic, it's all pretty easy to understand once you get some basic info.