I am a former Trinitarian. I now believe there is only one true God, whom Jesus called “the Father.” Therefore, I no longer believe Jesus is God, as Trinitarians believe and as I formerly believed. But, like nearly all Christians, I believed that mostly because that is what I was taught. Also, there are some differences in critical New Testament texts in major English Bible translations. That is, in these texts in some of these translations, they say Jesus is God; yet in other translations these texts do not say that. It depends on what the Greek New Testament and Hebrew Old Testament say or mean.
The Bible says God sits on a throne in heaven. How should this be understood? Trinitarians believe God is spirit, and they presume from this that God cannot have form. I don’t think Trinitarian theology makes that restriction. Thus, a Trinitarian can believe, as I did, that God has spirit form (e. g., John 4.24; 5.37), thus incorporable. But most Trinitarians think this means physical. No, being incorporable can be restricted to spirit, as with angels. So, I also believed as a Trinitarian that angels are not physical beings, yet they are incorporeal as spirit beings. That is, angels have spirit form. According to the Bible, angels sometimes literally have appeared to humans. When this has happened, they always appeared human-looking. But they could appear and disappear instantly, just as the resurrected Jesus did according to NT gospel accounts.
Trinitarians often say God is not incorporeal. They mean God is not a physical being. Well, I certainly believe that. But that is not what incorporeal means. Incorporeal means “not consisting of physical matter.”
I believed as a Trinitarian that God in incorporeal by literally having form and sitting on a literal throne or throne-chariot in heaven. That is what Jewish merkabah tradition teaches in accordance with 2 Kgs 22.19-23, Ezekiel 1, Dan 7.9-14. As a Christian, I would add Rev 4.2. It all has to do with understanding heaven as a spirit place.
Yes, I believe heaven is an actual place outside our universe. The Bible often says God resides far “above” the earth. It says God looks “down” from his location in heaven to see people on earth. I do not think we should try to change the meaning of such language, as if God is speaking in anthropomorphic terms that need be deciphered some other way than as we would literally comprehend it. And God’s Spirit is not God himself. God’s Spirit is universal; but God in his person occupies a literal place. That is how Jesus could constantly say, according to mostly the Gospel of Matthew, “my Father who is in heaven.” Thus, God in his person is not here on the earth; rather, he is in heaven and sometimes literally sits on a throne there before his angels.
About thirty years ago I had a written correspondence (seven letters each) with DTS President Dr. John Walvoord that involved this subject among others. It centered on how we should understand the “horses” riding out of heaven at the parousia (Rev 19.15ff). He wrote, “there are no horses in heaven.” So, he concluded they are not horses at all. And that’s what he says in his commentary on the book of Revelation.
That reveals how most Christians think about this subject. That is, they assume horses must be physical without considering the possibility of them being in the form of spirit in heaven. And it’s the same for God. This discussion can involve other entities mentioned in the Bible, such as angels, four living creatures in Ezekiel 1 and Rev 4.6-8, cherubim, and seraphim. In my view, they are all spirit beings, heaven is an actual place, and heaven is a spirit place.