Can I change how it looks?

A little. Trailwise has one light look and no theme switch. On Settings > Display you can set row height, either standard or more rows, and that is saved: it applies to the training log on the Agenda and to the readiness table. On a phone it changes nothing, because those tables already reflow. Units, distance format and date format are shown on the same page but are not saved yet, and the page says so rather than pretending. Do not expect to switch to miles yet.