Yea, every shield in the mix of the cleaver duct tape will also trigger the cleaver chain once, so 3 shields are 3 extra activates. The issue is, that despite no attack triggering, you will still recieve the - damage from shield spirit in the mix. This usually means nothing tho,s ince a single activation already triggers many belt of knifes for all cleavers. But it can work against you, if you have more pavis than cleaver.
There is definitely some min maxing, also in the way duct tape priority works. For example a cleaver with rage and a cleaver with golden whetstone. I saw a change in damage by swapping around my cleaver, so I would assume that the position in the duct tape line matters and buffs will be used in realtime instead of calculated beforehand. In a big cleaver chain my logic would be to have it trigger rage as early as possible to have as much cleaver beneifit after it. The whetstone cleaver could be in a positon where it would mostly hit at the highest damage of belt of knifes.
If you use duct tape, the position of shields won't matter. In a chain of duct tape, a common blue cleaver is better for it's 1 extra damage than any other cleaver, as long as the sideways activation is not necessary to trigger a cleaver that isn't part of the same duct tape.
With belt of knifes tho, the only real thing that matters is how many cleaver activate in one turn on the same duct tape. If you can get energy, every single energy will increase your damage by a huuuuge amount. I can't even test the damage of my third hit, because my 2nd hit already does triple the damage of my first hit. Every extra energy would mean insane damage, but it is very hard to come by.... and .. you are really glad if the cleavers finally stop attacking :D