I don't know who has been telling you drafts eat "insanely" more, but they don't; most drafts eat less than smaller horses, or the same amount. In my experience, feed them too much, and you end up with a walking sofa.
I've ridden a belgian and I own a draft cross; both have been very smooth to ride, and I preffer riding them than smaller horses, but I may just either not be picky, or of gotten comfortable rides.
I know nothing of showing, so I can't help you there.
Drafts are usually very gentle and easy to train; if you're new to horses, I recommend you do NOT get a "project" draft. Their size alone makes things harder. If they spook, they're harder to control; if they're tied, they can easily break loose; if they step on you or kick you, it hurts a lot more. Mind you, most drafts are very level-headed. I'm just warning you.