I've got the 200mm Metzler and I think it looks really good on the bike. I can't speak for handling since mine was on it when I got the bike. I was a new rider when I bought it back in the spring and had no problems with it but looking back it may have slowed my learning curve some at slow speed stuff.
I don't have info on the 200mm tire thing, but check these guys out for the digital speedo/tach. 've been running one of their round units on my Bandit for a while, and it's a really nice quality unit. Not too terribly expensive either. They've got a couple of US importers, or you can order from the UK and they'll ship it.