I have several auxiliary "close up lenses" but only one of them (Nikon 6T) is a chromatically corrected doublet.
The general formula is Magnification=Diopter Strength x Focal Length of Main lens (mms)/ 1,000.
So, the bigger the diopter or the longer the focal length of the main lens, the greater the magnification, but -of course- so also are the greater the problems, such as shallower depth of field and poorer resolution.
My observations using these add-on lenses are that: good hand-holding technique is most important (and can be improved with practice); the quality of the main lens is most significant; colour corrected doublets (such as the Nikon 6T) produce sharper images than simple lenses; the weaker the diopter, the sharper the image; and the smaller the aperture used, the sharper the image.
From this, it would appear that -for the same magnification- using a weaker diopter (such as a +3) with a longer focal length main lens (such as a 100mm) will produce a sharper, cleaner image than using a +6 diopter and a 50mm standard lens.
On the other hand, I have had quite "acceptable" results even when stacking a 55mm (good quality) standard lens with a good quality 2xTC and a (doubtful) +3 diopter simple auxiliary close-up lens.
These auxiliary lenses also work with zooms: for example, I have combined the Nikon 6T (+2.9 diopters) with a SMC Takumar M42 4.5/ 85-210 zoom and obtained very clear, sharp images comparable to dedicated "Macro" lenses (of which I also have several).
BTW, another "gizmo" that produces very sharp images is the 2x Teleplus Macro MC7 focusing tele-extender, used with a good quality 50mm prime lens: resulting in some really gratifying results, and so convenient to use.