CCN my child that is "most" visual spatial and definitely most sensory has no synasthesia at all and does not get it at all. She's been quite freaked out by the conversations about it in fact. That said she has impaired working memory, AS and is dyslexic and can't spell to save herself. I guess there is an extent that she is "more visual spatial" because this is a standout strength amongst her weaknesses. She does have an amazing visual memory and amazing long term memory.
My daughter with synaesthesia has a 140+ WM score (can't remember exactly what it was) and she actually has a higher score in the visual spatial than her sister, but her verbal is higher again than that, so her visual spatial skills are very strong but not her relative strength, if that makes sense? She certainly has learned to read and to spell in a completely different manner and on a radically different trajectory to my eldest. You would expect that from the difference in their IQs and also given my older daughter's other Es (she's definitely one for the E/e thread), but it is interesting to wonder about the impact of the synaesthesia and differences in memory style/function between the two of them.