My 17yo has High-Functioning Autism - we live near WDW and have visited often since he was born, so we've found lots of ways to make it work. Primarily, it's a matter of limiting overstimulation time - crowds, noise, visual overflow, he just can't take more than a couple ours of it at a time. Meals help give him a break, and we rarely do more than 4-5 hours in a park at a time. Quieter attractions are good breaks, too: the Seas, Living with the Land, wandering around countries in EP, walking the trails or doing the safari in AK. Until Galaxy's Edge opens in DHS, there isn't much there that interests him, so we keep our time limited there, though Sci-Fi is a great spot for a meal to decompress. MK is the hardest park for him, and he's usually done with it after a couple hours. He brings noise-canceling headphones and will wear them as needed.
We used to just skip anything with a long wait, but recently asked about
DAS and found it to be helpful: my son was able to do some rides he enjoys that we can't usually get FPs for because they're gone by the time our 30-day window opens.
As his mom, the hardest thing for me is guessing when he's hit "ENOUGH." Heat + crowds + noise + inadequate food and/or hydration is a bad mix, so I just try to remind him to eat and drink, and when he starts seeming agitated, I get us somewhere quiet. If quiet and food/drink don't help, we bail and head out.