I’m not sure about the evidence base for altering pedaling technique or L/R balance as some kind of efficiency improvement. I’m sceptical that it would make a big difference to most riders.
In terms of training benefits - single-sided vs. dual power readings shouldn’t make a big difference to the accuracy of your training as long as you remain consistent. Single sided power is L-side x2 which may not be entirely accurate but is at least a consistent basis for the workload you are doing.