I struggled with social skills when I was younger, but once I had a diagnosis I spent a lot of time learning them and now I have the moves to execute them, so long as I conform to neurotypical ideology.
Processing sensory stimuli takes effort for me. If there's more going on than I can safely process, my ability to perceive, think, and function will degrade. This includes noises, lights, textures, conversations, and noticing things around me.
I can protect myself by erecting sensory barriers that exclude certain stimuli from my perception, but they take work to maintain and they aren't perfect, and they can lead to not seeing important things (which is dangerous when driving a car).
I can create a fascilime of a neurotypical person for people to empathise with, connect to, and socialise with. But when it comes to sensing my genuine feelings, neurotypicals are simply less able.
I cannot understand certain patterns of neurotypical thought. I can mimic them perfectly, but I can't think them. Whether to blindly copy others is a choice.
Neurotypicals struggle greatly to understand my patterns of thought, unless they have a great deal of patience.

As an autistic person with NPD, I can tell you from direct experience they're very similar in terms of how they influence my relationship with society. Autistic people struggle to understand my narcissism, narcissistic people struggle to understand my autism, neurotypical people struggle to understand everything about me, and I get along great with other autistic narcissists, of which there are not many.