Happy 2020 everyone and congratulations on the New 5-10 flashlights we’ll prolly buy in 2020. 
This Nitecore charger can use 5v-2a or 9v-a usb chargers. It’ll also use QC2.0(Quick Charge 2.0). Anyone just using a 5v-2a UCB charger without QC2.0? Can you still get all the max settings for the charger? I don’t really want to buy a 9v-2A. I have so many good 5v usb chargers laying around.
Nope, you won’t get Max 2 X 1.5A without a QC 2.0 charger. You will only get Max 2 X 1.0A.
And QC compatible varies… For eg, My Samsung S9+ & S10+ charger does not provide the UM2 with 9V. Only at 5V.
While my old Samsung S7 charger works well with the UM2 @9V-1.8A.
Ahh shucks now I gotta think all day now 
Does one need 2a for charging?? I actually got 2 chargers now. The Opus 3100 I use for things that take a long time like refresh. Whereas the Nitecore I’ll use for charging mainly. So should I buy another charger that has QC2??
It depends on cells specs and individual preference or comfortable level how one gonna charge his cell.
I have 4 chargers. Up to Max 2.5A. But my preference and comfortable level are charging my cells at Max 1A. I have no rush to charge them. :) :) 