I have not grown autos, but I have a bit of experience with FIM anf TOPping. Two TOTALLY diff results. When you TOP, each cut will sprout two new shoots, so you plant gets wider, but you still have some branches/bud sits LOWER on the plant\\thus FURTHER from the light, right?
When you FIM, IF it works, that is..you get something like a candleabra or Menorah...four, five or maybe six stalks THE SAME HEIGHT, arranged side by side. In other words, imagine a single stalk from whih four -six shoots emerge...side by side, equal distance from the light.
Prob is, FIMming aint easy...OR totally predictable. Ya gotta LEAVE about a quarter of the GROWING TIP, wheras, in TOPping, you cut or pich off the WHOLE growing tip. IF you carefully cut off 3/4 of the growing tip of your main stalk and if the Green Goddess smiles on ya....you may discover 4-6 NEW shootsINSTEAD of just TWO.
Again, I dont know much about autos, but Im guessing the rule holds true. Plus, IF you screw up....no big deal---you will STILL get the usual TWO new shoots, as if you had TOPped.
:! I leaned to FIM by accident. I had a young plant siting on my deck rail while vegging. My cat, or maybe the wind...knocked it off and that plant fell two stories to the ground, BREAKING off the main stalk,l but by chance, LEAVING about a quarter of grow tip. I could not believe tyht plant even survived the fall...let alone when I noticed FIVE new shoots coming out of the break.....each one growing to become the same height as the others, giving me five 14" long buds at harvest. When it works...FIM is great.