To some extent, it depends on where you live! Didsbury High is a new school and linked to Cheadle High and, like WHGS, has a very small catchment area. Parrs Wood is quite a distance from Burnage, if that’s where you live, so not many local children go there, it’s also very large and has a mixed reputation re behaviour.
From your description of your child’s needs, you need to be asking what arrangements the school could make around his possible need for access to smaller spaces, quieter areas and clubs to support friendship issues. Any large school might feel the same to him - a scary space with large play grounds, crowded corridors, noisy dining rooms etc so it’s the accommodations the school can make that might be important.
Does he have any support from the SENCO at his primary school? If so, they should be helping him with the transition - he might need extra visits, access to a safe space, different lunch arrangements or a buddy system.
Have you considered the new Chorlton High South near the the Police building on Mauldeth Rd? The staff there have lots of experience from the original CHS with catering for students with additional needs.