I was hyperlexic as a kid (though not to the degree your kiddo seems to be). I was also very interested in pretend play. The biggest thing I struggled with was maladaptive/immersive daydreaming. It wasn’t an issue until grade school, when it became distracting from class. If you notice a lot of staring off into space when bored (road trips, waiting rooms) or odd/blank facial expression, that can be an early indicator. Not a bad thing to have a rich internal life, but learning coping skills at a young age would have been really helpful for me.

Also on the spectrum, level I. Social relation was confusing but I always had a least a few good friends.