Deactivating RF modulator circuit, should I cut off the supply voltage as well?
You do not need to remove E232 or R237. They will not overheat, in fact they will dissipate less power with X2 removed.  If there is no complete circuit for the current to flow then the resistors will not dissipate any power.  R237 will still dissipate some due to R238 still being in the circuit.
You can verify that the resistor is not dissipating any power (or very little) by measuring across it with a voltmeter.  If it says 0V, then there is no power dissipation in it.  If it has some voltage, the equation to calculate power \$(P)\$ in a resistor \$(R)\$is:
$$ P=\frac{V^2}{R}$$
Where \$V\$ is the voltage measured across the resistor.