photos? finally succumbing to the dark side?
All about your setup and how you water them. Since you have a rez setup, you can use prefilled 1 gallon coco bags like the ones JP is/was using. Plants can/will get huge in that size with proper automated water/feed. If you wanna use your pots, personally I'd go 3 gallon to start. If hand watering go with the 5 gallon
As far as transplanting, either way. I usually start in solo cups on a heat mat and transplant around 2 weeks. You can chuck them in with your autos while vegging. Then transplant into final home for another two weeks in before flipping. If regular seeds, I transplant into 1 gallon till sex shows.
A million ways to do it