Hello,
I think you can definitely run the two 2000s in a 4x8. Each 2000 has a 4x4, 3x3 range and if you hang em just right they should be able to cover the area you need well enough, especially during veg. Technically during flowering your light coverage would be 6x6 so you'll lose 1 foot on each end. With choosing the tent size, i would think of how much moving around space you might want or need.