1) Anything that shrinks as it cools. More it shrinks, more it helps to have heated chamber (shrinkage: Nylon > Polycarbonate > ABS > PETG > PLA).
2) Nylon, Polycarbonate, ABS
3) Having controlled heater inside helps.There is a thread on that topic somewhere. Cheap $15 personal heater stuck inside suppose to help a lot.
4) From what I heard, standard behavior of the Dreamer is melting in high temperature. You really want to have all metal guts on your printer if you do heated chamber.