They will draw wax as they need space. During spring buildup they want to expand the brood nest. So they build comb. During a flow,they need comb for storage, so they build. If conditions are right, feeding will stimulate them into expanding the hive. You have a slight tight rope to walk if your feeding syrup. You will need to make sure they don't backfill the broodnest and force a swarm. In the fall they will build little comb and drdicate the stores for overwintering.
1:1 is the best mix to simulate the nectar flow. Just be sure to remove the syrup if your planning on a honey harvest.