Without chopper stabilization, flicker noise is dominant @ low frequency. We might want to increase the aspect ratio (W/L) and also device area (WxL) of the input transistor. Also, it is necessary to push the mirror transistor in the saturation region and this should be accomplished by increasing the L of the mirror transistor.
With chopper, assuming the corner frequency of the flicker noise is much lower than the chopping frequency, we can safely assume that the flicker noise will be fully removed by the chopper amplifier system. Therefore, in the amplifier design, the objective is to reduce the thermal noise of the system. The reason for this is that the noise spectral density after chopper application can be approximated by noise density of the amplifier at chopper frequency. One way to achieve a lower thermal noise is by increasing the transconductance (i.e. gm) of the input transistor.
Pnoise simulation should be able to simulate a chopper stabilized system.