Not all of them are, Blue! Mine is a right lazy slug. I know some very very quiet Anglo's. I also know some completely mental Anglo's, and some in-betweeners.
Monty has his moments, he's very bi-polar actually... it's like having 2 totally different horses rolled into the one package. One day he'll be a lazy old bugger and the next he'll be so full of himself I can barely control him. He's bolted with me a couple of times and taken off with me more times than I can count, but not for a while. He bucks sometimes when he gets TOOOOOOOOOO excited but nothing I can't handle... I think he's bucked me off once, thrown me at a gallop once, and then dropped me at the base of countless fences, all through my own mistakes. His "I'm too excited and just HAVE to buck and run fast" fits never unseat me. He's thrown in some pretty epic spooks, including several 180-degree spins (with me bareback, in slippery jods, on a wet horse with a slippery coat/back), all of which I've stuck on easy enough, so his behaviour isn't an issue, but if I screw up, I'm almost guaranteed to eat dirt.
I think the heat of the cross depends on the horses used. If you use a highly sensitive TB and a highly sensitive Arab then you're asking for trouble! I like horses that are generally reliable but have some get up and go when you ask for it... making my boy nearly perfect because he'll fall asleep in the start box and then wake up with a squeeze and a click and be in full flight in 2 seconds flat and less than 3 strides. I can heat him up with halt-to-canter and walk-to-canter transitions, or chill him out with walk-halt-walk-trot-walk-halt rinse repeat. Or, more quickly, I can heat him up instantly by giving him a tap with a dressage whip! That puts him straight on his toes. Only complaint I have is that it can take him a long time to chill out once I've heated him up.
Monty is amazing... totally versatile do-anything kind of horse.
....do you want my TB? At this rate she's looking like being something else for sensitivity and forwardness. Not crazy, in actual fact she's a fairly quiet horse, but by god does she respond to the tiniest aids! She's not broke yet because she's 2 and also because I'm struggling to find a breaker who is tactful enough for her. She doesn't cope well with discipline. Took weeks for me to be able to so much as tell her 'no' without a huge panic attack.