The NGK washers are nicer quality than the cheap crud that comes with Chumpions or Oughtta-lites. They do come off without much hassle; you grab the outer rim of the washer with a regular pair of pliers and just unscrew the plug out of the gasket. It's worth doing, too, which is why Chrysler said to do it. See here. The '63-up heads have a redesigned counterbore at the top of the spark plug hole; the spark plug tube itself seals the plug, and if you use the washer it interferes with heat transfer from the plug to the head. The '60-'62 heads don't have the special counterbore and need to use the plug gaskets. This is factory info; following it has always produced best results for me. The idea is to prevent the plug from running too hot; following factory procedure and going without the ring washer means you can dial in just a tetch more timing 'cause your engine is just a tetch less prone to pinging, well, you're that much ahead.
And no, the 3459 (ZFR5N) is not a peanut plug. "Peanut plug" means the taper-seat plugs used on '75-up slant-6 heads. The 3459 does have a small hex (11/16") rather than a large hex (13/16") but the only difference that makes is you have to use a different spark plug socket to install/remove them.