Blueberries are usually planted in large containers, like half-barrels (real wood or fake). Berries and a lemon tree will mature into larger plants and need more room for root growth. I use smaller smart pots for annual vegetables, like green beans and cucumbers.

The smaller the pot the smaller the plant will be. The smaller the plant the smaller the fruit yield. I personally wouldn't use anything less than five gallons for any of those. But, I would recommend you use the largest ones you think you'll be able to handle and move around as it it will be necessary at some point. What's the advantage of a smart pot? Isn't it just a brand of fabric grow bags?

Definitely go for the largest pot you can get.