Son just diagnosed

Hi. My 7yo son got diagnosed with ADHD last summer and based on that assessment they decided to do an ASD assessment. We had the outcome yesterday and he has autism which were quite surprised about as it seemed like a lot of the questions we were asked during the assessment were not relevant to his behaviour. 

I don't have the full assessment report yet but we were told it's related to social communication and transition times etc. He was diagnosed with SPD 2 years ago too. I'm very new to this but it seems like my son is high functioning as he is very sociable and is articulate in the way he speaks he just struggles to understand how another person is feeling and doesn't understand when to stop something another person does not like but thought it was more ADHD related. 

Just wondering if there are other parents out there with high functioning autistic children and how subtle the traits are? Sorry if I'm not using the correct terms as very new to this!

Thanks