Lot of questions about this matter can be cleared up by defining "personality" as Webster did in his 1828 dictionary:
"Personality: That which constitutes an individual a distinct person." In the context of the times, i.e., Kellogg's "Living Temple", which spiritualized the nature of God, EGW contended for the distinct individuality/personhood of the Godhead. That's why everything in Adventism hung on that doctrine. It signified the actual individuality of the persons of the Godhead, opposing Kellogg's spiritualizing of God's nature. Reading Kellogg's comments, they remind me of the Chinese concept of Qi, an impersonal life force which actuates human beings, as opposed to a personal God. EGW was arguing for a personal God, intelligently involved in the life of his children.
[My opinion today, as a hobbyist]