INAV sits in the useful middle ground between FPV-oriented flight firmware and heavier autopilot stacks, particularly for GPS-assisted fixed-wing and long-range RC builds. A major release candidate is the point where experienced users can start finding hardware-specific regressions before stable release.
Do not treat RC1 as a routine production upgrade. Back up the full configuration, read target-specific issues, remove propellers for bench checks and verify motor/servo mapping before flight.