Do 2000 bitrate 720p60.
The FFXIV community on twitch has become rather small and a large number of viewers watch on cellphones/tablets/etc. 2000bitrate for FFXIV only yield a small amount of visual noise during very movement intensive scenes, but it won't be enough to distract away from an otherwise solid quality broadcast. At 2000, your retention rates will be a lot higher due to people actually being able to watch without buffering.
Fair warning, your follow count will grow quickly on FFXIV, but your quality per follower won't be very high -- that is to say, any amount of time you spend on any game that isn't FFXIV and any time a more established broadcaster is live you'll see your numbers drop significantly. FFXIV viewers generally follow anyone who streams FFXIV consistently and are typically much more loyal to the game than to any particular streamer. While follow numbers look nice, it is an incredibly superficial number that has no effect on anything.
Despite what many people will tell you, as well, raid content isn't good unless you supplement it by creating usable resources for viewers and attract people to your channel by other means than just broadcasting this game. There are FFXIV streamers who are among the best players across any server you could name who get no views -- and the serious raiders who make up the top of the list are not there just because they are big into raiding.
Lastly, if you just want to stream just for the fun of it -- focus on that and it can be great. If you're doing it trying to get big online, I'll say that 1) FFXIV is not the game for that for reasons I listed above, and, 2) you're going to be a little careful with stuff like pre-made videos on your channel.
SOURCE: I'm a full time streamer/content creator, built up my old channel almost entirely on FFXIV, and I'm the Team Captain/Coach for 2ARC Gaming's stream team.
Anyway, good luck and have fun.