You lose a layer of safety when you don't balance while charging lipos. If the balance wires are not connected to the charger, charger has no way of seeing a problem at the cell level where the prob will start. It may be too late by the time the total voltage gets far enough out of spec for the charger to react and do anything (shut down). There has been one case documented here of a lipo incident in a guys bedroom which was damaged that would have been prevented if the balance wires had been connected. Always balance charge.

Lipo Fast mode and regular lipo balance charge mode differ by the CV period of the charge. Since lipo typically receives 85-90% of the charge in the CC mode, the fast mode stops charging at the end of the CC mode or shortly after the start of the CV mode so you wind up with about ~90% charged lipo.

Connect the balance wires anytime you connect a lipo to your charger.