4 layers Design- Using polygons
I would complete the PCB routing this way:

PCB Grounding

Fill the empty areas of PWR, TOP, and BOTTOM layers, with copper connected to the GND layer. Use many stiching vias all over the board connected to the GND layer.
See this picture. It's full of stiching vias:



PCB copper cage for containing RF spurious emissions caused by fast raising and falling edges currents.

Add a copper border all around the board.
Add stiching vias connected to the GND layer all around this border with a step of 2.5 mm.
See this:


Stiching vias can be big. Example: drill 0.4 or 0.3 mm, copper pad diameter 0.7 or 0.8 mm.