35 to 40 DLI will be max you can give over 12 or 18 hours per day or 24 for that matter, given ambient co2. this varies. feeding properly, temps and rh matter too, as far as maximizing available co2 use.
same things you'd have to worry about with a young autoflower. if doing 12/12 from seed it'll be fine. ramp up light as it matures. allow the distance between growth nodes dictate that process.
35 dLI over 12 or 35DLI over 18 will have same effects on plant. if it is too much over 18 it'll be too much over 12.