“Do you view the Powers of Waincraft as distinct beings, or simply as “ideas” or archetypes. For example, is the Lord of the Green literally a god sovereign over growing things, or is he just the personification of growings things?”
Short answer is both.
Literally, the Lord of the Green is the Power of life in all its forms, but most particularly cyclical life, of which vegetation is the most abundant. Symbolically, he personifies the cycle of life that grows and falls and rises again.
The Powers of Waincraft are fully immanent and integrated with the physical realm. Thus they are both spiritual beings that control and direct natural and cultural forces, and the impetus behind and manifestation of those very natural and cultural forces. Orthopsychy applies to all of existence, the Powers included.
A true archetype can exist in its own distinction as well as echo itself in other distinct beings. There is nothing simple about either an idea or an archetype – they are both powerful, complex, and utterly fascinating creatures.
Is a Mother not a distinct being from all other Mothers, while still sharing an essential commonality that differs only in its particulars? A Teacher can teach history or common sense or magic, and the style of that teaching can and will differ depending on subject and personality, but they are still a Teacher.
It is a poor tribute to Jung that one of his finest achievements has been so twisted by pop psychology as to completely change its meaning.