After market lowering involves constant rate springs with adjustable lower perches to achieve the majority of lowering.
The correct way to provide additional minor lowering (and increases camber adjustment range in dedicated race cars mostly) through camber-caster plates is with a variety of single piece spacers of varying heights on the strut shaft; below the bearing sitting snug on the shoulder of the strut, and above the bearing under the strut nut.
The spacers are very strong material and the correct diameter to snug securely on the strut shaft with no play or eccentric runout. When bolted down properly, the spacers act as "one piece" with the inner bearing ring in between the strut shoulder and top nut. There is no play at all, only the bearing itself. Here there is only a clamping compression/tension force physically fixating the strut to the bearing as a solid piece, there is no opportunity for lateral or sheer type forces as those are solely between the strut shaft and bearing (much like how lug nuts and wheel studs only hold the wheel to the hub via tension, they don't bear the vehicle weight or cornering forces if torqued properly)
You do not want spacers in the mount plate, only a single washer between the tower and the bottom plate to allow it the plate to tighten down against the strut tower while allowing for minor tolerances in the sheet metal.