That is totally up to you. If you feel it is more important to give the gratuity directly to the staff go ahead and do that. There will be NO problem in having the auto tipping taken off your sail and sign card. If you feel they a different amount than the auto tip you can increase or decrease the auto tip with no problem. If you feel they deserve more you can also leave the auto tip and give an envelope with more to those you feel are deserving.
The only advantage of auto tipping for the passenger is the fact they do not have to try to carry or find the cash to put in the envelopes and you won't see the staff holding their hands out on the last night.