Would the Yamaha FG700S be too big?

Any dreadnought sized guitar like the 700S is very big. I'm a grown man and they even feel big to me. You will get used to it, but you might want to look for something in a Grand Auditorium size instead. I honestly can't tell you any models off the top of my head though. Your best bet is to just go to a store and see what they have in your price range. I know some of the more expensive Taylor's and Martin's come in a smaller size like the Auditorium and the 000C.