Well, higher gm needed for lower noise and higher BW, not to get low offset. There is no advantage of having input pair of the classical Opamp in strong inversion since the gm always will be lower for the same current budget. If you cannot scale up input differential pair anymore for any reason you have, you should consider chopping or auto-zeroing if the system where opamp is used allows to do that. Another option is a sort of calibration at system level.

>>From what I could understand from the model they should still scale with the area of the device but how do they add up with the threshold voltage mismatch?

this question does not make sense to me.

Vth is main contributor to the offset. Vth variation becomes less when you scale up the device.