Good question. I was born and lived on and off there for a total of 11 years, till about age 20, so I didn’t really study deeply --only more so as an adult, but I absorbed enough mentality (it was about 97% Muslim), that it’s been an interesting subject.
Sunni do tend to have more of a simple view of God, but even that’s not as simple as it looks; the Qur’an, as you know, says that Christians venerate Mary, Jesus, and God the Father, rather than the Holy Spirit. One version of what we believe (from their point of view) is that God had relations with Mary, or had more of a true son–like the Greek pagans. It’s a bit of an abomination reaction they have, as we would, to that sort of melding of God and human natures (as though God were a breeding thing). So, the oneness is reactionary by definition, I think. Talking with some Muslims then winds up unfruitful because we have different definitions in mind–they think we’re believing something rather awful, and we think they think we believe something different–it’s a bit comical, sometimes. Phil Parshall https://en.wikipedia.org/wiki/Phil_Parshall and https://answeringislam.org/God/index.html have been helpful to me. (not that I’ve read it all). The fact that the Byzantine Empire created “byzantine” as an adjective for the complexities of our attempt to understand Jesus’ nature indicates to me that God is more forgiving than we are about our understanding!
It’s not quite as simplistic, to my understanding, with some versions of Shi’a and many Sufi, some of whom border on the pantheistic (the Pentecostals of Islam).
I know you have written about Islam–congratulations! It’s a deep subject. Maybe you can comment more, and teach me more.