G'day,
the Langematik Perpetual for sure is a nice choice for an automatic Lange!
I think you can´t do wrong with one of these!
In terms of the folding clasp, in some way it will fit to any Lange model.
Just get a strap that is made to fit the lug and clasp width; for example, ABP in Paris or Camille Fournet support custom orders made to fit your preferences (colours and materials included).
But then, i´d rather choose the watch first and then get the matching folding clasp

Usually the width of the clasp is choosen to balance the watch case dimensions and weight, therefore i´d guess the wearing comfort will improve if choosing the appropiate combination as offered by Lange.
Cheers,
Peter