Noise in Audio (DFPlayer) when adding LED strip
The source of the noise is the PWM controlling of the WS2812 LEDs within the stripe. Their PWM frequency is approx. \$1\,kHz\$ (some say \$400\,Hz\$), what is audible for humans.

The first fix is to add a electrolyte capacitor close to the terminal of the stripe. Chose a \$\ge470\,\mu F\$ cap with a voltage rating from at least \$\ge6\,V\$. You even can use several caps in parallel.

The next step is to filter noise on the player supply lines.
Therefore use a resistor of \$\approx 100 \Omega\$ and again a cap \$\ge100\,\mu F\$ with again \$\ge6\,V\$ voltage rating. If you have inductors available replace the resistor with a solenoid. The suitable equation for determining the values is \$f_{Filter} = \frac{1\,kHz}{10} = \frac{1}{2 \cdot \pi \cdot \sqrt{L \cdot C}}\$

If you do not have inductors and there is still noise, you should consider to supply the DFplayer with a separate USB cable from the USB hub.