Missouri Fox Trotters/Mountain Pleasure Owners!

My horse, Dillon is a quarter horse/Missouri fox trotter/mountain pleasure mix. He is mainly quarter horse, so you'd expect he'd be beefy and calm like one. However, everyone thinks he's a thoroughbred,. He's very delicately made with a very thoroughbred face. 
He's also nervous too. Part of it is that my legs are the strongest ever, according to my trainer, but he's also just naturally more wary than most horses. 
My trainer and I know nothing about Missouri fox trotters or mountain pleasure horses. I've tried to find things on them but it says nothing about their personalities.
So I'd like to know from owners of those breeds if the horses are nervous horses or not. Because Dillon does not think he is quarter horse at all lol

I don't own a Missouri Fox Trotter or a Mountain Pleasure horse, but I did do some research and Missouri Fox Trotters are the prime choice for trail riders, so they have stamina, a good nature, and they are very relaxed.

Mountain Pleasure horses are lively, friendly, and intelligent from what I've researched as well.

Quarter horses, I do own, and they are sweet, muscled, quirky, and calm for the most part.  We've had some stubborn QHs but they are all pretty calm.