Benefits of trimming ?

I have 8 plants (the doctor) which are really bushy I am on week 4 what's the benefits of trimming or should I just let the go ?

id say trim the bottom at least...usually the bottom branches have the smaller buds...if u trim and make it look more like a tree instead of a bush the bigger buds up top will grow more and i think you will be happier with the outcome...just my 2 cents...good luck

or you could trim upper leaves that are blocking light to lower branches

So how do I go about trimming where and what would I trim ? I've read not too touch fan leaves ?