I generally wait until true leaves form, but when breaking up a community pot, several plants are often at the more immature stage. I never notice any particular difference in growth, so am not sure that the formation of true leaves really matters. I notice some of your plants are very close together. IMO, the larger that you let them get, the more entwined the roots will be. So probably earlier repotting of those might work better.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.