Your thread size isn't really a pure wheel matter. I tend to do very thin things on a lot of wheels with no issues, yet a high ratio is slightly more comfortable as it doesn't make you fight the bobbin.

Size is more a matter of fiber prep and process I believe. I find combed tops work way better than carded stuff with way less shortcuts leftover grass and overall inconsistencies distracting me. Tension must be fine tuned as you go, I think our wheels heat up a little at the bearings and you must compensate that, fines doesn't behave the same way on rainy days than they do when the sun is shining and you have to consider that too...

But also little tricks to compensate the higher impact in twist variation on finer spinning like pulling all my singles from tensioned bobbins to place them on a skein winder several meters away to smooth the tension for several hours prior to putting back on bobbins with the same several meters distance before plying...