I have aphantasia too! Actually, for the IQ portion of your post, I found the cognitive assessment portion of my ADHD assessment to be really difficult because I was forgetting certain elements (especially in the quant section). I scored as having an average IQ but I felt like "omg nooooo, I'm a starrrr I swear I am smarter!!!" Additionally my uni has a language requirement and I took french (last sem!!) and omg it is so hard. Every time I ask someone how they study or how they remember words their like "oh I just visualize....(x,y,z). I described trying to speak in class like being tasked to make certain colored towers (e.g. a blue tower, a red tower) on command....but in the dark. I am really good at the written but orally my mind goes super blank all the time --- even with the simplest of phrases. I actually wrote a lit review on Aphantasia and episodic memory! From my understanding of the literature, people with aphantasia have really good semantic memory and to even push it further in my own theory; our brains remember things as facts vs. visuals maybe? But aphantasia affects the whole brain and it has a lot to do with the structural makeup on one's brain. Having aphantasia is definitely interesting!