Swarm has 3 days food with them. Somethimes I have feeded at once and they may escape from hive in that method.
When bees are settled down, after 3 days you can give 20% syrup. They build combs in a week and sugar is spended in work. If you give 50% syrup, they will store it.
When swarm is basket ball size, it will occupy 1-1,5 lansgtroth box. It is good size. It depends, if hive has old queen or virgin queen, how it starts to lay eggs.
If 2 boxes are not filled with bees, it is wise to get another swarm and put them together. So you will get honey and a good hive at once.