I am going to try and offer another approach to the original question: Is Heidegger a Conceptualist?
The notion of Conceptualism is historically located in the Medieval debate about universals, which stems from attempts to interpret Aristotle (particularly Porphyry's interpretation of Aristotle) and his antiPlatonic line on categories (and forms).  As opposed to Realism which refers to things, Conceptualism refers to our understanding of things.  The alternative approach to both is Nominalism - we are just talking about words or flatus vocis ("puffs of air") as Roscelin and Abelard claimed.
Heidegger does not involve himself in any of this debate as far as I can recall.  His many references to "basic concepts" (Grundbegriffe) need to be understood in terms of his rejection of the realism / idealism debate; Heidegger saw what he was doing as, "... neither on this side nor on the far side of idealism and realism, nor is it either one of the two positions.  Instead it stands wholly outside of an orientation to them and their ways of formulating questions (History of the Concept of Time, p.167)."  So, Heidegger was seeking to, "preserve the force of the most elemental words (Being and Time, p.220)."
What Heidegger was after was a closeness to actual scientific exploration as Aristotle conducted it and from which philosophers have distanced themselves ever since (without realising it).  He even called his own early phenomenology "primordial science."
What is interesting is that Heidegger interprets Aristotle as having this same methodology - hermeneutic phenomenology.