AFAIK all host softwares available have a "Flow rate" setting. I personally never touched that.
An Extrusion Multiplier setting is different from flow rate in terms of calibration.
Cura has it's built in slicer.
Repetier uses external slicers like Slic3r. Slic3r has this extrusion multiplier setting. This is not a host software feature.
Of course you could calibrate your Filament Width setting (ex. 1.75mm ->1.6548mm).
What I use to do in Slic3r is to enter the average filament width (1.74~1.73) and then print hollow boxes to calibrate via the extrusion multiplier.
I think the extrusion multiplier is then used to calculate all the other different line widths that are generated.
I am not sure that an adjusted flow rate does the same. Also I don't like to mess with flow rate settings to calibrate a print. I think this somewhat mediocre. I don't know. It just doesn't feels right.