(I have nothing to add to the question…)
Yes it can, provided you press the button to signal USB c output before you plug it into the device being charged. But keep in mind it will not charge it in docked mode
While PowerCore+ 20100 should charge your Switch, as @elmo41683 said, your best bet - at least as of right now - is going to be PowerCore+ 26800 PD. This model supports much faster charging through Power Delivery. Hope this helps!