If you are not a fan of mechanicals and don't want to deal with mushy membrane keyboard either, Scissor switch units are your best bet. They are quieter than even the quietest mechanical MX-style switches and their low travel distance feels comfortable without being squishy.
PBT is polybutylene terephthalate, which is harder and has a slightly better hand feel than POM. The keycaps are not easy to be oiled and have a stronger graininess