Switch-mode power supply and EMI on input power line filtering
A "typical" two-stage power supply EMI filter looks like this:







simulate this circuit &ndash; Schematic created using CircuitLab

The inductors attenuate common-mode noise (and also offer some differential attentuation via their leakage inductances). C1 and C4 shunt differential-mode noise. If there's an 'earth' point available you will also see two more capacitors between CM1 and C4, connected from each rail to the earthing point. These provide more common-mode attenuation.

Sometimes you will see a single stage, sometimes two. As long as your filter is attenuating the necessary noise components and are OK thermally, I don't see a pi filter being 'wrong' necessarily. (For lower frequency conversion, it's easier to get the attenuation via the inductors - just add more turns / more core etc.)