All critical functionality is available without the Pro subscription, including all of the live data, logging, ride history, custom shaping, etc.
Even advanced features such as mapping, configuration alerts, fully customizable runtime alerts, Apple Watch integration and many more are included in the basic version.
Here's some features exclusive to Pro subscribers:
Faster Logging
Premium Hermes Integration
Live Charts
Heat Maps
Home Screen Widgets
Live Activity Widget for your iPhone lock screen