Starting out for veg you’ll wanna be 24-30 inches 30 for germination and seedlings then you can lower it to 24 after a bit! Once you get into flower you’ll want your lights 12-18 inches from the canopy!! Good luck and happy growing! 👍🍀
I go by leaf temp, especially once roots have set, usually three weeks into the grow. Nothing over 28 degrees Celsius, then whether the spread is good enough.
What’s the tent size? For veg I’d try 24” and she has she likes it. If she stretches lower the light if the leaves start to frill you want to raise the light. But tent size will matter a lot.