Reality is a word that has two opposite meanings:
Sentient being's subjective reality, known in the modern semiotic science as "Umwelt", is the world a sentient being finds itself in: a world of a frog, a world of a bat, a hell, and so on. This is what Pali Canon refers to as a "loka".
The objective or ontological reality, is the supposed basis or ground underlying the subjective experience, common to all the different perspectives and interpretations and giving rise to them.
Historically, Buddhism had difficult relationship with this second type of reality. The Buddha famously described The All in terms of subjective experience (the seen, the heard, and so on) and refused speculations about the metaphysics, leading some students of Dharma to think that Buddhism denies any objective reality. Indeed, the dhammas in their narrow technical meaning — Abhidhamma's fundamental building blocks of reality — are expressed in terms of their phenomenology, they are things like solidity, wetness, hotness and so on. At the same time, early buddhist texts speak about "external forms" and describe consciousness as something dependent on the body, so it seems clear that Buddhism is not a form of subjective idealism.
That said, I don't remember a historical text, whether EBT or Mahayana, that would explicitly define or use a concept equivalent to what we would call ontological reality. When we hear that all dhammas are empty, or impermanent and deceptive, or that their existence does not match their appearance, we kind of understand that we are talking about subjective reality vs ontological reality, but no Pali or Sanskrit text ever uses such terms. Perhaps bhava (existance) comes close but it refers to existence of each individual thing, not all of them as in "reality". Another word I can think of is "dharmata" but it refers to the way things work not the way things are.
Back to your question whether it's dhamma or sankhara that refers to subjective reality, it is neither. Just like bhava, dhamma refers to each individual phenomenon, not the overall Umwelt of a sentient being. Sankhara is even less fitting, since it refers to the objective composition of phenomena in the ontological reality of causes and conditions, not to appearance.
So I guess the best Pali word for what you are asking about would be "loka", a world sentient being find itself in.