Hi,
If you have experience with EMC/EMI you already know very important things.
I strongly recommend to use a complete layer just as GND plane. No copper fill, no routed traces within the GND plane.
Place all filter capacitors as close as possible to the signal destination, with short wiring to the GND plane.
The shorter the traces, the better. Trace width is not that problematic.
The smaller the whole PCB the better. SMD components. Round or square PCB is better than a lengthy PCB.
Traces that are in parallel to the magnetic field lines ar not problematic, but 90° to magnetic field lines are.
If possible: use a metal (Fe) case.
Klaus