When to transplant?

Id do before the transition into the Veg stage. These is when you will see your stem split and make and opposite set of growth. This is when your plant leaves seedling stage. So, anywhere just before that, I wouldn't leave too much longer after that. I'm not a fan of growing in dixy cups full stop. They hinder air getting to the bottom of your soil. And can build up with fluids. Poke a few holes if you haven't. But, really just uppot it and it'll be good to go. After your veg is done. You can go ahead then a uppot again for pre flower. This will cause an explosion in top growth I've found. Don't leave it too late. The week before you flip. Uppot that way if there's any stress. You can ride it out until you know she's 100% as if it's a long veg. She might be root bound. You'll need to break up the roots lightly at the end to help root expansion again. It'll cause stress. But a few days and she'll be back at full tilt. Then get your LST points set, defol if needed. Not too much. And never defol during pre flower "the stretch, upwards growth".. dis takes roughly from 14-21 days. You'll know when Calyxs start to form and upwards growth nearly comes to a stop. Good Growing.