I am using samsung tab s6 lite. I want to know does it support 20W fast charging? The 20W fast charger is from a different brand (motorola). Will that be any problematic in the long term?
It depends on the charger, what standards does it use, it is PD, QC, and which version. It may say something like QC 2.0. And have a voltage and maximum current output. All that will depend on what power delivery method your phone chooses to use from the charger.