The bodice should be cut, like a vest, with built in armholes and shoulders, never as a camisole-type cut with straps. It can have a square or rounded neckline, which is always cut across the top of the nipple line, not higher. If you want more modesty, wear the smock higher or wear a partlet. The neckline should also never be cut below the nipple line. The result is not period, and it is both uncomfortable and an eyesore.
Most bodices lace up, but they can also be fastened with buttons or hooks and eyes.
The technique of fitting body curves with darts had not yet been invented. Rather than have clothing conform to body curves, it was constructed in such a way that the body conformed to the clothing. It is very important that the bodice be sturdy and closely fitted enough to hold the figure in. Too many bodices are made out of one layer of light fabric, with lightweight lining. A proper bodice needs an inner layer or flatlining of canvas or other heavy fabric to look right.