This is a personal theory only, but for what it’s worth..
I think there are two fundamental ego types – The Candyfloss and The Softcentred Chocolate.
The Candyfloss – has a woody and well defined spine, around which is constantly spun a fluffy melting sweet floss where it contacts the world. This creates a fuzzy boundary which invites fusion with others. But… the ego melts and is in danger of falling apart but is rescued by the clearly defined core.
The Softcentred Chocolate – has a brittle and well defined exterior which defends the soft inside. Will one break ones teeth on a hard toffee? Dare one bite in? It’s only on intimacy that one discovers that the inside is meltingly delicious.