They can all be different.
Typically, to obtain the effect of a small feedback capacitance, C1 is the smallest.
If C1 << C2, C3, then the effective feedback is less than C1, and there is an additional input capacitance of approximately C1.
The tee network is exactly equivalent to a pi network (using those equations) and independent of frequency if all impedances are the same type (capacitor, inductor, or resistor).
Also note that the op amp must be happy driving the series combination of C2 and C3 to ground (not too huge).