I finally played through Hollow Knight some months back and really enjoyed it. Just a marvellous game. I do enjoy metroidvanias but they can also be a bit of an investment sometimes, so I'm always a bit hesitant to start a new one.
I'm not sure if Maddy's older games are harder than Souls titles or not. They're very precise and that would be difficult for a lot of people. On the other hand, Souls games (at least the more recent ones) are more reaction-based, and that presents its own difficulties. I think either could be difficult for people with low motor control, but both skills can also be improved through practice.
I've played so much of both that I really don't have that beginner's context necessary to evaluate it fairly anymore.
I played through Celeste 64 after finishing the C-Sides in the regular game. I really liked the Mario Sunshine-esque stages. Overall though I was content to put it down after the hour or two I spent with it.
I saw one of your SM64 runs on my Youtoobs. I recognized some of the tricks, like the backwards bomb carrying. It seems like a tricky but very fun game to learn speed tech on.