Within breeds of horses, there are different personalities, just like with people. A lot of people think that ALL draft horses have laid-back personalities but that isn't necessarily so.
I can say from my experience, that my draft colt (part clyde) usually thinks before he reacts, is overall calmer than my light horses but that could be just him, not the draft in him. Another thing I've learned since he grew extra large is that they do generally cost more money to maintain. He eats more in bulk than a regular horse, although he doesn't need more nutrients; it costs more to get his feet done and it can be hard to find a farrier willing to work with your horse; I've had to special order his tack because you can't find a 62" girth, draft size bits, bridles, etc. at most tack stores and I'm currently in need of a new horse trailer because he's too tall for my average horse sized trailer.
He is pretty easy to handle but we've done all the groundwork and stay on top of him so he doesn't learn how big he is and get pushy. He is very smart and learns quickly. I'm taller than average and I do have to use a step stool to groom the top of his back, saddle him and get on so if you are little, that could be a problem.
An older (over 10 yrs. Old), already trained horse with a calm personality could be good for someone with low confidence as long as they had a trainer to guide them.
One thing that is against a beginner owning a Clyde is maintaining their feathers and the health of their skin underneath them. They look wonderful in pictures but you really have to know how to care for them.
Do your homework and find a reputable breeder and go in with your eyes open. How's the little spotted pony working out??