Just got a HTC one m8, have some questions about the keyboard
There is no way to disable autocorrect on the default HTC keyboard. I had this problem too and tried a few keyboards just to be disappointed with most of them like you. I settled on the the Google Keyboard as it has all the functionality of the HTC one, including typing suggestions and emojis (and I like its design).

The emoji issue may be fixable with this app but you need root for it. I have not tried it myself but some of the emoji packs seem to be in-app purchases.