As Trinitarians Christians often, and rightly, refer to the inner reality of God’s singular life as his ousia or ‘being.’ The fear might be that Christians might be imposing Hellenistic (i.e. classical Greek philosophical) categories onto God thus morphing him into an tertium quid, or even worse something completely alien to who he actually is. This is the critique I often bring against classical Calvinists in their deployment of Aristotle to articulate their Pure Being theology relative to the Christian God; I don’t think they are successful in allowing the Revelation to determine the language’s shape; I think they carry over too much of the Aristotelian philosophical implications in their endeavor to give grammar to articulating God for human understanding. As such, I think they eschew everything else downstream; i.e. whether that be in the area of doctrine of creation, theory of revelation, theory of history, doctrine of Scripture, soteriology, so on and so forth.
Us Evangelical Calvinists, like classical Calvinists (and other iterations of classical theists), also use the Hellenic language of ‘being’ and ‘persons’ (hypostases), among other expressions. But unlike—and here I’ll just keep picking on the classical Calvinists—the classical Calvinists, or as Richard Muller calls it, the “Christian Aristotelians,” we follow Athanasius’s style and mode in regard to allowing the antecedent and ontological reality of God’s life to give shape and reify the Hellenic language of ‘being’ and ‘persons’; our intention is to allow God’s Self-revelation to retext the Hellenic language in such a way that the language’s meaning itself becomes brand new (recreated even) because of the new context it finds itself in (since context determines meaning anyway). Thomas Torrance explains how this worked out in the Athansian mode:
Athanasius much preferred to use verbs rather than nouns when speaking of God as the mighty living and acting God, for abstract terms or substantives seemed to him (as indeed to the biblical writers) to be inappropriate in speaking about the dynamic Nature of God, or in expressing who God is who makes himself known to us in his mighty acts of deliverance and salvation. For Athanasius, here as elsewhere, the precise meaning of theological terms is to be found in their actual use under the transforming impact of divine revelation. This is how he believed that the words ousia and hypostasis were used at the Council of Nicaea, not in the abstract Greek sense but in a concrete personal sense governed by God’s self-revelation in the incarnation. He preferred a functional and flexible use of language in which the meaning of words varied in accordance with the nature of the realities intended and with the general scope of thought or discourse at the time. Hence he retained the freedom to vary the sense of the words he used in different contexts, and declined to be committed to a fixed formalisation of any specific theological term for all context which might have violated his semantic principle that terms are not prior to realities but realities come first and terms second. This intention is nowhere more evident than in his cautious and differential use of human terms to speak of the Being of God or the Subsistence of Persons in the doctrine of the Holy Trinity.
Us Evangelical Calvinists go with TF Torrance and Athanasius; particularly when it comes to the idea that the reality precedes and thus should be allowed to control the terminology in its context and sense.
If you ever wonder how Evangelical Calvinists can use the language of ‘being’ and ‘persons’ and not fall prey to the same temptations as the Christian Aristotelians, refer to this post.
One more important point in closing: If we get our doctrine of God wrong (which includes very much so how we employ theological language), then everything else following will be eschewed. This is why Evangelical Calvinists place such emphasis on our Trinitarian Doctrine of God as the ground and grammar of everything.
 See Richard Muller, Post Reformation Reformed Dogmatics, Volume Three (Grand Rapids, Michigan: Baker Academic, 2003), 45, 62, 107, 121, 132, 140, 150, 367, 545, 553.
 Thomas F. Torrance, The Christian Doctrine of God: One Being Three Persons (London: Bloomsbury T&T Clark, 2016), 117-18.