Light height and intensity question.

best you can get is a maybe... several factors equate to how many photons in 24 hours a plant can handle without issues (and even that is compartmentalized to surface area.. e.g. you can't just blast some of it with the total) so, observe and react... take notes. It may not even be exactly the same each time you do it, especially if your region has seasons or enough variation in temps and RH to cause a difference. At this early stage keep a close eye on internode length. Are the growth nodes stacking on top of each other with really tight leaves and not 'stretching' out a bit? if so, it's too much light. Are the internodes lengthening so much that the plant is weak or the stem turns pale? if so, this is too little light. These are the extermes, but if you see behaviour leaning one way or another, it's a good guide to giving the most light without damaging the plant. What you refine over time will be fairly consistent from grow to grow, but always observe and react. VPD is important, atmospheric CO2 is important... these things vary for most of us... the goal line will shift slightly given new parameters, but will be close unless you do somethign dramatic (like control temp, rh and add co2 to 1300ppm etc... i wouldn't bother with the co2 unless you do the other 2 things as well as generally doing everything else in an optimal way or you'll just waste some portion of the extra co2).