Since you are not in a SCROG and it looks like you are doing some super cropping it may need a while to heal first before you want to bloom it. It all comes down to the height. think about where the light can be at its highest point. then subtract the distance needed for that type of light and that is the max height your plants can get. Then measure your plants height. again since it can triple in size you want to make sure that the height from the top of the soil to the top of the plant is no more than 1/3 of the height left in your grow space. That may still be too much because you may not have the horizontal spacing needed to get that high properly. But assuming you can space them out properly and knowing you don't want them to grow into the light and hermi you want to start them at 1/3 the distance to that peak spot.
I am not sure what you mean by "trimming". There is an advanced technique based on some pruning that you shouldn't be doing if you are asking these questions. If you are talking about taking clones that is something I like to do right about the time I flip the lights to bloom cycle personally but that is a personal thing. You can clone at anytime and it is more about how you want to raise the clones and how much grow space you have.
If you are talking about taking off fan leaves in general, that is not a recommended practice for a number of reasons.