We feed all 3 of ours live, and none of them are aggressive in the least. They're puppy dog tame. But, it's up to you, whatever your most comfortable with, and of course, how your snakes like to eat. Some only eat live, some only eat FT, some eat anything and everything you give to them
Where did you read that? I've learned to only trust what people say on this site. You'll also read that feeding them inside enclosures makes them "cage aggressive", which is also a myth.
I've read on here that people separate the spine of the rat from the brain (or something like that) by holding the head and giving the tail a good yank. It's supposed to be quick for you and painless for the rat (or mouse). I've never done it, so I could have just explained that wrong. If I did, someone will correct me and give you the right way to do it.