Dr. Leighton Flowers (a former 5-Point Calvinist) speaks about this often. Check out his writings and podcasts if you're interested in more information or to hear from former Calvinists. He and his guests often speak about pre/post views on Romans 9, Ephesians 1, and John 6.
I've included an example of his prior/post interpretations of Matthew 22:1-14. While a Calvinist he viewed these as one combined choice, now as three distinct choices the King makes:
- Choice of His Servants from His own country, given a task of sending the invites.
- Choice to send the invites first to His own country and then all others.
- Choice to allow only those properly dressed.
- Israel for which the Law, His word, and Servants would be sent (Rom
3:1-3, 9:4-5). Not because they did anything (Deut. 7:7, Rom 9:11)
- Israel and Gentiles, all “bad as well as the good”
The above are the “many are called” - this is not about individuals being chosen to salvation.
- Those clothed in righteousness of Christ through faith. The choice is anything but unconditional.
“Few” and “chosen” are those who responded freely to the invitation through his unconditional chosen servants from his unconditional chosen nation.
Verses like John 15:16 or Paul’s encounter are linked with Choice #1, not with Choice #3.
Choice #2 shows that its sent to all, not ‘some individuals but not others’.
God is granting or enabling faith or repentance by sending out the invites to all.
Regarding Calvinism one should look at history:
John Calvin wrote, "Augustine is so wholly within me, that if I wished
to write a confession of my faith, I could do so with all fullness and
satisfaction to myself out of his writings."
"This is why one finds that every four pages written in the Institutes
of the Christian Religion John Calvin quoted Augustine. Calvin, for
this reason, would deem himself not a Calvinist, but an Augustinian"
Cary concurs, writing, "As a result, Calvinism in particular is
sometimes referred to as Augustinianism."
Augustine was a Manichaean for 9-10 years, prior to his conversion. Augustine "taught traditional Christian theology against determinism for twenty-six years prior to 412 CE. When Augustine started fighting the Pelagians he converted to the Gnostic and Manichaean view and taught that humankind has no free will to believe until God infuses grace, which in turn results in saving faith."
Although earlier Christians taught original sin, the concept of total
depravity (total inability to believe on Christ) was borrowed from
Gnostic Manichaeanism. Manichaeanism taught unborn babies and unbaptized
infants were damned to hell because of a physical body. Like the
Gnostics, the Manichaean god had to resurrect the dead will by
infusing faith and grace. Augustine changed the cause of total
depravity to Adam's guilt but kept the Stoic, Manichaean, and
Neoplatonic concepts of the human dead will requiring god's infused
grace and faith to respond
In this pagan group, a non-relational God unilaterally chose the elect
for salvation and the non-elect for damnation based upon his own
desires. Early church fathers prior to Augustine refuted non-choice
predeterminism as being pagan.
These systems believed that the material world is created by an
emanation or 'works' of a lower god (demiurge), trapping the divine
spark within the human body. This divine spark could be liberated by
gnosis, spiritual knowledge acquired through direct experience.
Sources (additional contained within links):
 Calvin, John. A Treatise on the Eternal Predestination of God. in Calvin, John (1987). Calvin's Calvinism. Translated by Henry Cole. Grandville, MI: Reformed Free Publishing Association. p. 38.
McMahon, C. Matthew (2012). Augustine's Calvinism: The Doctrines of Grace in Augustine's Writings. Coconut Creek, FL: Puritan Publications. pp. 7–9.
 Cary, Phillip (2008). Inner Grace: Augustine in the Traditions of Plato and Paul. Oxford, UK: Oxford University Press. pp. 122–124.