I make all my smoothies using garden of life whey protein powder (120kcal, 0 fat, 6g carbs, 24g protein). I would not recommend substituting plant based protein because it changes the consistency and the flavor. If you do still want to use plant based, it will not be as thick and potentially not as sweet, so I would recommend adding more banana to counterbalance. I also use iced green tea for my morning smoothies, but you can change out with water or milk if desired.