Ditto what @SternWake said.
It may be a little cheaper and more “elegant” to get a single supply can do multiple voltages, but don’t overlook the human error factor. Chances are you’re going to be recharging your stuff hundreds of times, so even being 99% on top of things isn’t enough.
If you ever forget to adjust to the right voltage before plugging in your PEV, best case you don’t have a power supply anymore.
Worst case you don’t notice, and it charges your 12s pack up to 20s voltages and you don’t have a battery anymore (or possibly a house)
IMO, Using an adjustable psu for charging in a pinch is fine (heck, I’ve done it a bunch), but it’s best to have dedicated chargers for regular charging. (Also lets you to charge stuff in parallel, from two separate circuits)