>>Is there a clear line where the "scottish English" finishes and "scots" begins or vice versa? I think there is a continnuum. The people in Scotland speak varying degrees of Scots-ized English language (depending on geography, education, social situations etc.) rather than are distinctly divided between "speakers of scots" and "speakers of English". Or am I mistaken?<<
There is not really a clear line, because while there is clear Standard English and clear Scots, there is a wide range of variation with respect to Scots-ization of English dialects or, conversely, Anglicization of Scots dialects, and the same individual may speak a full continuum of varieties ranging from Standard English to Scots. Similarly, there are almost certainly no monolingual Scots speakers today aside from the very young and the very old, and then only most likely in remote areas and like at that. At the same time, Scots itself is not a set of English dialects even if few today probably actually speak "pure" Scots; it clearly as a separate phonology, lexicon, syntax, and so on from English dialects even if even Scottish Standard English has clear Scots influence (particularly with respect to phonology).
For a similar example, what you say makes me more think of the situation in northern Germany, where there is Standard German varieties, dialects of High German influenced by the native languages of northern Germany*, and the actual native languages of northern Germany. Most people today do speak Standard German, and when they don't they largely speak High German with Low German or Ripuarian influence. Only a small portion of the population today really speaks "pure" Low Saxon or like anymore, and practically all of those individuals also speak varieties of Standard German or at least other High German dialects. At the same time, that does make Low Saxon, East Low German, Ripuarian, North Frisian, and East Frisian "German dialects" any more.
* that is, Low Saxon, East Low German, Ripuarian dialects, North Frisian dialects, and East Frisian (that is, Saterland Frisian)
There is not really a clear line, because while there is clear Standard English and clear Scots, there is a wide range of variation with respect to Scots-ization of English dialects or, conversely, Anglicization of Scots dialects, and the same individual may speak a full continuum of varieties ranging from Standard English to Scots. Similarly, there are almost certainly no monolingual Scots speakers today aside from the very young and the very old, and then only most likely in remote areas and like at that. At the same time, Scots itself is not a set of English dialects even if few today probably actually speak "pure" Scots; it clearly as a separate phonology, lexicon, syntax, and so on from English dialects even if even Scottish Standard English has clear Scots influence (particularly with respect to phonology).
For a similar example, what you say makes me more think of the situation in northern Germany, where there is Standard German varieties, dialects of High German influenced by the native languages of northern Germany*, and the actual native languages of northern Germany. Most people today do speak Standard German, and when they don't they largely speak High German with Low German or Ripuarian influence. Only a small portion of the population today really speaks "pure" Low Saxon or like anymore, and practically all of those individuals also speak varieties of Standard German or at least other High German dialects. At the same time, that does make Low Saxon, East Low German, Ripuarian, North Frisian, and East Frisian "German dialects" any more.
* that is, Low Saxon, East Low German, Ripuarian dialects, North Frisian dialects, and East Frisian (that is, Saterland Frisian)