Parameter modulation, like any FX parameter move (including moving a knob on the GUI or moving a physical controller), is sent once per buffer block, that's unfortunately not something that anybody can change. Well-designed plugins will interpolate parameter moves internally to avoid zippering, for example if a filter plugin advertises "smooth sweeps" that's what they mean. For volume and pan parameter modulation, JS/utility/volume_pan does internal smoothing. If you have a plugin that you want to modulate but you hear zipper noise, you will need to lower the buffer size.