I've clearcoated a handful of playfields and they have all been in 2K. If you prep it correctly, use the correct clear and the inserts are glued in properly there should not be any issues.
As for the metal plate? Hmm. I would probably mask around it as it may cause a few headaches.
I have not done any clear in acrylic, although I've seen some work of a member on AA who does some exceptionally nice work and has had great success with it.
