Fruit development is a process taking place from pollination to maturity. Stresses at almost any point during the process will effect the final product. Stresses include nutrient level and availability, water (too much OR too little), soil pH, root mass (directly related to pot size), soil temperature, air temperature. Appropriate pot size is dependent on what the mature size of the plant is. Most pepper plants require a minimum pot size (container) of 5 gallons (19 liters) to grow without undo stress. I like using 20 gallon (75 liter) containers. This allows for ample root development and irrigation frequency is lessened.
Thanks for swift response.