I might be able to chime in here as someone who's studied, experienced - first hand - and taught other professionals about to a good level, although I'm no expert, only an expert by my experience. I was diagnosed with BPD which as with other personality disorders, can be viewed from different perspectives, medical, psychological and psycho-neurodevlopmental and other various schools of thought in the field of psychotherapies.
One approach I found interesting was an explanation given by Jeff Young, creator of Schema Therapy.
en.m.wikipedia.org
Is his model he suggests the concept of Schema Modes which when placed on the spectrum of dissociation, from weak to full blown DID you get a good idea of how it's possible to experience "partial" - to use your words. Young's model offers an eloquent explanation and supposition of the experience of dissociation that people who fit a certain cluster of other symptoms fit perfectly together.
Modes is just one part, the main are adaptive and maladaptive schemas or beliefs which form the early foundational basis of an infants early days supported with ideas borrowed from people like Melanie Klein
melanie-klein-trust.org.uk
Klein supposed a way to understand the psychological development with inherent challenges that young infants endure. This is what therapy is about to integrate the parts that patients always bring. To deal with reparenting. Mostly it works but for me, my early models are so pathological I cannot override even when I dissociate...
I love this subject.