The tricky thing about graphene is that it is really, really, thin. It only takes a few sheets of graphene to out-perform a kevlar vest, but you could in theory make it a million or even a billion layers thick, and still make a quite comfortably thin and light weight armor material. In other words, you can make it as much stronger than modern armor as you want as long as you are willing to spend the time and money making it that thick.
The real limitation is how much force can be transferred through it. Once you get past a certain thickness, the graphene will hold up against almost anything, but the person inside will be turned into blood pudding from the impact force. This means that the best design will be to layer the graphene over whatever distributes the impact the best. Currently non-newtonian fluids offer the best impact distribution for their weight.
In short, you are looking at what modern body armor already looks like, just with a hundred or so layers of graphene to reinforce it.