Design of the two stage amplifier with p-type input
You can regard both types as complementary, if the circuits are identical but one is just the "upside down" version of the other, everything applies to both architectures you only need to watch the directions of currents and voltage polarties but that is it.

Lastly, what is the difference between these two architectures?(in general)

They are identical but one is just the "upside down" version of the other.
Think about this for a while and you'll see that they're the same architecture wise. The only reason for using the P-input stage instead of the N-input stage is the (commonmode) voltage range of the input voltages. But that is a property of the circuit. If one has an input voltage range of 2 V to Vdd, the other will have an input voltage range of Vss to (Vdd - 2 V) (assuming all NMOS and PMOS are completely complementary).