My Bubba was 23 days from sprouting in the last photo posted.
5 gallons should work for you, others like Nugs use 3 gallon (3lbs kind to 3gallons), and that may be sufficient for an auto...can't say for sure if 5 gallons is too much since this is my first Kind grow. My other grows in coco/perlite were in 5 gal., and the root systems had no problems filling those smart pots quickly! Your future seed selection is ambitious...wish you well on those. I did white widow auto as my first grow, and it was a charming variety! 😊