It's dependent on a few factors but as long as you have enough roots/space/light you can have 20 tops no problem.@Bill284 how many top sites is too many top sites I mean would you cut all the lower top sites that didn't make it up to the top of the canopy to make sure that you don't have any unmature bud
Trimming the bottom third of the plant is common.
It has been labeled Lollipoping.
Post strech approximately 20 days after you initiate flowering.
I remove anything below the light line that's just going to suck energy and not amount to anything.
I found this pic.
Gives you an idea where to trim.
But I don't trim any upper fan leaves, let them stay.
You don't need to be as aggressive as this pic shows.
Stay safe
Bill