I hadn't tried to connect to twitch in a long time, and I had similar trouble as you, until I finally got the combo they want. There may be other setting which also work, but I used:

address = irc.chat.twitch.tv
port = 6667

TOP PASSWORD = oath:oathstringgoeshere

login method: SASL (/CAP)

bottom password = leave blank

As I understand it, the top password is for servers that require the password before even allowing you to connect, while the bottom password is for stuff like nickserv.

Once I connected, I did get a couple of errors, but I doubt these are fatal, other than I don't have the correct CAP commands set.

USERHOST Unknown command
LIST Unknown command