Many growers think you should not top/fim auto as to not introduce stress since the plant only lives around 3 months. In reality, that is a false statement. I trim / train many of my auto plants.
As a grower, you know the health of your plant. Healthy plants fare well. Unhealthy plants will suffer. If the are healthy, top them before the FLOWERS COME...this is the PERFECT TIME to trim. Remember, only trim a small amount...then feed...
Frankenstein auto above
lemon haze auto below
GSC auto - from a 1 gal pot
these are just a few...I grow auto mainly with a few photo here and there. I like the variety, simplicity and for a 1 gal pot, I can grow 50 in my tent (4x8x7 tall)