I guess the easiest way to implement a conditional operator is to add a quantum register ($cond_0$) that will contain the conditional parameter and then have a succession of control-gates, controlled by $cond_0$.
In your case lets's call A, $Op A$ and B, $Op B$. $op_0$ and $op_1$ will be the registers involved in $Op A$ or $Op B$. Obviously the same reasoning works with operations on more than 2 qubits.
The conditional quantum circuit is then :
from qiskit import QuantumCircuit, QuantumRegister
import numpy as np
from scipy.linalg import expm
A = np.random.random((4,4))
A = expm(A*A.T*1.j*math.pi/2) #"whatever unitary defines operation A"
B = np.random.random((4,4))
B = expm(B*B.T*1.j*math.pi/2) #"whatever unitary defines operation B"
#register acting as the conditional statement
qr1 = QuantumRegister(1, name='cond')
#registers involved in the operation
qr2 = QuantumRegister(2, name='op')
qc = QuantumCircuit(qr1, qr2)
gate=ex.UnitaryGate(A, label="Op A").control(1)
gate=ex.UnitaryGate(B, label="Op B").control(1)
The resulting circuit is:
As you can see if $cond_0$=$|0\rangle$ then $Op A$ is not applied but $cond_0$ is bit-flipped so $Op A$ is applied.
In the same way if $cond_0$=$|1\rangle$ then $Op A$ is applied but $cond_0$ is bit-flipped so $Op A$ is not applied.
The last bit-flip on $cond_0$ is done to restore the value of $cond_0$. (Potentially unnecessary)
Hope that helps.