What do you mean by "convoluted medical terms"? You'll need to know basic med terminology; my job required me to go through 100 hrs of training, including classroom and on-the-job training, before I started going solo as a scribe. That training included learning and taking quizzes for medical terminology and abbreviations, differential diagnoses, and physical exam findings.
Many of the docs do talk fast, especially when they're telling you orders to input, but you also get faster as a scribe over time. For the system we use (EPIC), I free-write the HPI and ROS/PEx is clicking buttons + free-type comments. We also have "dot phrases," which are custom preset phrases we can insert into the chart. There is downtime, especially when you move from trauma/medical side to fast-track, but that's depend on patient volume and the doc you're working with.