The weapon focused G5 PD can run four lasers (I do it on my Cutter). For three lasers, a G5 charge enhanced suffices if you keep 4 pips in weapons, but I anyway put weapon focused on it so I can run 0-3-3 more or less continuously throughout the session. The main advantage of the charge enhanced is that you can use it for essentially anything if you want to repurpose your ship, the weapon focused distributor still almost allows perma boost, but boosting is not the main thing of a mining build anyway.
For the OP, running three lasers is possible with both weapon focused and charge enhanced at G3 so it comes down to what he wants to do with the module later.