I fully agree with EGW's take on this. We as limited, fallible humans, cannot fully understand the nature or essence of God until we are like He is. When we face things we cannot hope to fully understand, we create mental constructs (admittedly based on our partial understanding) in an attempt to wrap our heads around facts we cannot fully understand.
I have heard the trinity is like an egg - it has a white and a yolk. They are two separate elements; but both are necessary to make an egg. I have also heard the trinity described like a fruit pie. It needs both a crust and a filling to be a pie. They are two separate elements; but both are required for a fruit pie. Furthermore, you can slice the pie into several pieces. Yet it remains a whole pie. Eight pieces in one pie is equivalent to three Persons in one God.
While these examples are extremely simple (even sophomoric), they make just a much sense, yet have many of the same limitations as the more sophisticated theological models presented above.
What is the salvational message here? To me, it is that there is more than one aspect (or Person) of God - a Father, a Son, and a Holy Spirit. Does our salvation hings on whether or not we believe in a Trinity or a "twinity"? I think not. Does it matter whether or not we believe Christ was capable of sinning? I think not; fact is He didn't sin. I don't fully understand the "nature" of my computer or my television, either; but I believe that they operate as advertised when used in accordance with the instructions ("commandments").