Topping and Fim'ing is best done in veg...
Topping is for...if the plant is getting tall with no side branches as it will encourage the branches out and depending on how much height you have.
Fim'ing will not only slow the growth in height down but enhances how many heads you get to flower. That fim cut can produce 2-6 New heads.
The plant needs at least 10 days to recover from the fim technique. That same with topping to notice side branch growth 😎