I'm not sure there is a strict date line for any of them. Singer had factories in US, Scotland, Canada and Germany, for a while in France too I think. The cabinet makers had standard catalog of products, but I suspect there where a few differences, more so on the cabinets than the machines themselves.
For example, I have seen model 28 and 128 in both types of cases. I assume they stopped making the 28 about the same time 128 where introduced (1910?), though I know there were at least a few years of overlapping in production. Maybe a change around this time? I have only seen the 99 in the smooth case (introduced 1911?), but I have not seen them all
My model 99 made in 1934 has the last type of case with the beehive handle.
For a long time I thought the suite case type in faux paper crocodile and similar paper or leather was a sign of a later date, I have seen a few from the 1930s, but even more common in the 1950s. Then there suddenly appeared a machine in a suite case type box, dating to just a couple of years after 1900, all was suppose to be original machine and case. Before WWI making paper was an art different from today, and came in many qualities just not made anymore. It's hard to know what they had available with out doing a lot of research, and even harder to sort out when the different types of cases and linings were introduced.
I'm just thinking out loud really.
I'm not sure when the domed cases entered the scene either, the older ones like model 12 come in both the more square type case as well asthe bent wood, already in the 1880s.