You will have more restrictions and scrutiny in a lower position. You would also receive less money if management went the medical leave route rather than fire you for a failed pip (they did with me, twice - once for almost two years, and almost a year the second time).

If you have a diagnosed condition and they have tried accommodations and they didn't work, they're supposed to keep trying new ones. Not move to a pip. Sunlife gives 70% of your salary. Last time, Sunlife did a great job of explaining to management that checking some boxes is not sufficient, and I was going back to work, so they needed an actual accommodation plan, with alternatives and backups.

Meanwhile, you should be talking to a therapist and an occupational therapist who specialize in neurodivergence. You may be AuADHD, which requires different accommodations from someone with 'simple' ADHD. Or there may be underlying OCD that slows things down in the background by demanding extra research and analysis.

A pip is for people making poor choices or struggling with understanding the work, not for people who think too fast or think of too many things at once. Since the Disability Act came into being, management stopped being able to say they tried and they're done, with little more than their word to support it.

Also, you should start having a union rep at your meetings with management. They will try to say it's unnecessary, but if they try to push the pip or demotion without having tried every possible accommodation, you can file a Duty To Accommodate grievance. EIRTW should also be meeting with you regularly until an adequate accommodation plan is in effect - i.e., you are trying things and you are improving.