As long as there is no current, slow is good.
If there is a strong current you must use enough power to remain in control of the boat. A center control point(center
line cleat) is very handy. If you tie up the center of the boat to the dock, it won''t move much until you can get the fore and aft
lines on. Also a rear spring
line is very handy. This
line runs from the outside end of the dock to the centerline point.
You come in under power, get the aft spring
line on. As that
line tightens it pulls you to the dock. If needed you can leave the motor in gear allowing you to go forward and get the bow
line secured.