lower fans that are not blocking anything should absolutely be left. sometimes you have to harvest twice when you scrOG , to ensure everything is finished and be aware lower flowers that you harvest second , allowing them to mature, will not end up with the same density as the first cut at least imo the stuff I let finish after a serious first harvest will finish. By finish I mean the trics will develop as normal. It you remove too many fans you will have a negative impact on yield (in my experience).