You would probably be one of the two smaller frame sizes shown. The only way to be positive is to go to your bike shop and be fitted. If you are buying a bike on line then you would expect to pay for the fitting. Bring the specs (tube sizes and angles) with you for the fitting.
The Merida shown is very entry level. Many consider Shimano 105 to be the least you want for racing. The shift action is more precise and the components are lighter. When you are racing you will find most other riders will be on Shimano Ultegra to Dura-Ace, and many on Campagnolo Chorus to Record.
Good enough to race with? Probably, if you are good enough. If you are good enough you will probably upgrade bikes within a season.
