m0useanswered grow question 2 years ago 18/6 is my go too.
I sometimes like to give them 24/0 or 20/4 as a seedlings first few weeks of its life but I don't notice a massive difference when I did it the one time.
Keep the lighting height in check, this is an easy way to burn plants when they growing up and not moving the light with them.
this is a voting poll on autoflower.net, grain of salt needed when reading it.
https://www.autoflower.net/forums/threads/whats-the-best-lighting-cycle-for-autos-24-0-20-4-or-18-6.3691/
Good Luck!