rijn said:
I flipped my stem (100mm 7 degree) upside down on my new road bike (transferred the parts). It feels very twitchy on turns and a bit on descents compared to my old bike.
Common experience with a new bike, but it's got nothing to do with the stem. How a bike feels in terms of handling is primarily determined by front wheel trail, wheelbase and rider weight distribution.
Because you're still using steering inputs learned and automated on your old bike, the new bike seems twitchy. After you ride the new bike for a while, you'll have learned and automated the new, more subtle steering inputs needed for the new bike—and you'll probably enjoy that new responsiveness very much.