Mild tasting garlics yield mild tasting rounds and strong garlics result in strong tasting rounds. For spring planting, rounds are your best bet to produce a good size bulb by the time early summer heat forces maturity. From a cook's standpoint, one large cloves means a lot less peeling, etc. Also, they seem to keep much longer than fully developed garlic, probably due to that heavy, thick wrapper they have. For more details please see the Growing Tips page of this website.
Most garlics harvest somewhere in mid season.
The larger they are, the longer it takes them to cure, that is, dry down. Wait for the leaves to begin dying down - the die down from the bottom of the plant first and then proceed to die down towards the top. When the top 6-7 leaves are the only ones still green and they're starting to look a little past their prime, that's the time to pull them. It is the heat that forces garlic to mature and we usually begin our harvest here in early to mid May and it extends into early to mid July. I would imagine your harvest would begin a month or two later than ours.