Did you top?
Otherwise, keep tying that big branch down. As for trimming anything, don't worry about it. Any fluff bud at the bottom can be used to make edibles.
Since you're three weeks in flower with pisils showing pretty good. She's past stretch. Let her do her thing.
Next grow, scrog her. Keep her flat so some buds don't get more light intensity then other colas. No worries on the bottom fluff.
[/QUOTim planning next grow to do a double net I bought from Amazon along with smaller pots. Any recommendation on how long to continue feeding before flushing?