Finally you provided some more relevant details, but not yet all. And my crystall ball is not working today.
Which speakers or headphones will play the music? What is their power consumption.
And which Arduino model? there are many with different power consumptions.
What you have to do is calcultate the maximum power consumption of all those devices in the worst case. Check the datasheets of all them.
But as a first approach, an arduino mini would need a few mA, the MAX9814 a few mA more. The DFPlayer Mini can consume about 50mA if I'm not wrong. The SD card other 100mA maybe?
Earphones usually consume less than 100mA, I think. But in the worst case with speakers it would be the 3W mentioned in the DFPlayer datasheet divided by 5V => 600mA.
So I understand that with a single phone charger of 2.1A or even 1A could be enough for all together.
Of course it all depends on your devices. If you connect a pair of speakers like the ones in the Maracana Stadium, then maybe 2A will be not enough.
After the calculations you can try and see if the music plays.