advice needed: How to pick optimal size smart pot

growing in a garage with 12 foot ceilings. Will not be doing vertical lighting due to heat issues. I plan on having only 1 plant per light (in order to keep numbers down). Will be growing them as big as I can (at least 5 weeks veg).

Im thinking 20-30 gallons smart pots per will allow for optimal size. Anyone have any advice?

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