enneagramtriad i think- a pdf. i have seen these kind of conceptualizations all over the place, i have 5 or 6 books but i get frustrated that it is generally not distilled enough to see cleanly. i'd just bounce around and let your intuition go to work.
and yes to everything you said. intj 5 would be perfect for enfp 7w6. 7 enthusiasm sells us when nothing else will. 8s are much more aggressive and they don't like feeling responsible for others. they loathe it and want total freedom to go after whatever they so desire. whereas 6s hesitancy and internal fears creates much more identification with the vulnerabilities of others.
i don't naturally see the 7 as gentleness, it doesn't immediately feel 100% correct like the first 3 do. but with more thoght i might start to see it. the enneagram theory adds so much depth to mb typings, plus it is MUCH MORE significant when understanding subjective experiences/past histories and development. mb is pre-scripted but enneagram explains what and why imbalances occur. it helps triangulate everything very very well.
it also shows how each type is a different psychological project. and it does WONDERS when explaining why we mistype people so often, how a 4w5 can be an infp, an infj, an enfj, an intp, an intj, and sometimes even an enfp or an isfp. they still are all getting at the same problematic, they are just processing it in different ways.