The difference between Dutch and German gets blurry when you go back a couple centuries. The Dutch part of Limburg was part of the German Confederation until 1866. The dialects in the Eastern Netherlands traditionally are mutually intelligible to their very closely related neighbouring dialects in Germany.
The division was pretty much just political rather than cultural or linguistic. Only with government-supported mass education and mass media and the official use of standardized languages on both sides of the border did the line between Germans and Dutch as two peoples clarify.
German for German is Deutsch, Dutch for German is Duits, Dutch for Middle Dutch dialects (time period 1200-1550) is Diets. In that time period neither Dutch nor German existed as standard languages but rather they were a continuum of dialects that had little to do with any modern territorial borders.
Hence a lot of names in NW Germany, both places and people, are very similar or even the same as in the Netherlands. There's a Bocholt in Germany and one in the Netherlands for example.
It is semi true even to this day... some people I know from Nijmegen have very little trouble understanding their neighbours in Kleve, and the same the opposite way. Ofc both their ears are more attuned to the other language as well.
As for Limburgers... they are not really Dutch. They cannot even speak Dutch properly...
You know they aint Dutch when they live on hills!
Part of Nordrhein-Westfalia was the Netherlands back then as well. (Bentheim.)
It is true there are a lot of names that transcend the border... names like Kessel, Boll and Snijder can quite easily be (and are found) from and in both.
Ofc things like Dijks, Vermeer, Kromkamp, de Jong etc are a bit easier... but could easily have been 'German families' settled in the Netherlands before 1811 who were then given Dutch names!
Most Dutch only had family names since 1811 though under Napoleons degree... so it is a bit easier than most countries to pick out those that are very likely to originate in that area. Before then most who had surnames used the -sen system. So it is a bit easier to pick out who is 'Dutch' from names since 1811... as those in Dutch territory at that time will have registered 'Dutch' surnames due to the dictate and its rules; but as you say it is still muddy in that regard, and many who were Dutch/German was less defined.
Though you also generally know if the person was born in 'Germany' in the Rhineland as opposed to 'the Netherlands' throughout most of the 1700s as the Catholic areas of the Rhineland were pretty damn good/meticulous with records, recorded on date of birth etc... and those born there would more than likely have a 'Germanic' first name if not surname.
Both those things make it slightly easier to say if there is more chance the family was 'Dutch' or 'German' after the 1700s by elimination, and after 1811 when both recorded very well even 'easier'... though still not perfect.
Toews is likely an example... being a Mennonite his family could well have been 'Dutch' but would have possibly had to leave the 'Netherlands' (which as you say in the 1500-1800's included what is now Germany, and the other way round as well) in the 1500-1600's depending on the 'province' they were from.
All I can really say is his name is not Dutch after the early 1800's... and very much more looks like a German name. (even before the 1800s there were differences... albeit as you say not much in certain areas; it is also quite possible the family did not even have a name then!)
But that does not say where his family is 'really' from (though that could go on and does ofc for thousands of years!)... but I would say I imagine his family emigrated from Germany to North America and not from the Netherlands.
It is as you say all very muddy across most of european ancestry.
Lodewijk van Beethoven
for example... 'Dutch' heritage but German! (gets even messier when you consider his family and name is from modern day Belgium.)
Other examples are Alsatians, Southern Danes and Northern Germans, Silesians etc... I have a Polish Silesian friend who considers herself 100% Polish... but has a name that is far more 'Czech' in modern day terms, and a German friend with a name that is German... but was changed in the 1800's from a Polish family name!
