Are you planning on going to the Wizarding World at both Universal Studios (London) and Islands of Adventure (Hogsmead) or just one?
Hogsmead is MUCH tighter and some of the shops are difficult to manouver in even on foot. The 'streets' are very tight also - which makes it look like the movie, but also makes it harder yo get around, especially with crowds.
The London area shops are still kind of tight, but there is a lot more open space outside, which makes things easier. The Knockturn Alley area of Diagon Alley is a bit more challenging - it's more twisty and dimly lit. It's really cool, but can be more of a challenge to get around.
Also important to be aware that many more of the Universal/IOA queues are not ECV accessible than at WDW. This is a link to their Rider's Guide, which should be helpful to you.
https://www.universalorlando.com/Images/Riders_Guide_tcm13-26195.pdf
Good luck to you with the new doctor. My son-in-law has MS. He is part of a study on oral drugs for MS and doing very well (he started before it was released). There are a lot more treatments and better treatments for MS than there were even 8 years ago, so hopefully, you will find one that works well for you.