I have used TC's plastic wad column intended for their New Englander 12, and some Winchester WAA12R larger volume plastic wads when waterfowling, with steel shot, bismuth (my preference for BP guns) Heavy Shot and other tungsten composite in my CVA double. I usually put an over powder card, then a commercial felt wad )for cups with no piston) before adding the cup, shot and overpowder card. With the TC cups, which I prefer because of their larger volume, I just load them directly over the powder with a card wad on top as they were intended.
I used to worry about lube, but for hunting I found there was not much difference and have dropped that added hassle, beyond the factory lube that may be on the felt wads, for waterfowl hunting.
The plastic wads protect the barrels, but I have also found that they will tighten the patterns to some extent as well, good for the larger birds and longer ranges encountered hunting waterfowl, like the Canada Geese so prevalent around here..
I don't mess with the plastic wads for upland hunting or target shooting though, and have used everything from hornets nest to felt wads to crumpled paper.
As far as cutting the piston off, I am with Griz44Mag. Try it both ways and see what patterns best for your needs. A little experimentation will help find what works.
I am all for sticking with traditional ways, but when it comes to protecting gun barrels and finding the most effective humane harvesting load for big tough birds, I bow to the plastic.