Once my plants reach the same height of the pot they're in, I transplant. Looks like you're ready, not mission critical +/- week. I like to do my transplant when the soil is nice and dry, usually the evening before they were due their normal water. Goodluck
Sure. They look ready for some fresh soil. New soil will perk them up in a hurry because the roots get a fresh supply of food from new soil and roots have room to spread.
Depends on how long veg and hpw long the strains flower. Aslong as they arent rootbound and can go through 2 wks of flower without binding i dont transplant i just kinda feed it like coco coir and can use full strenth nutes right off the bat