The base version of SIGNALIS (v1.0.0) is playable but suffers from frame pacing issues that ruin the immersion. The v1.4.0 update transforms the Switch port into the definitive handheld experience.
If you are a completionist hunting all five endings (Promise, Memory, Leave, Artifact, and Lotus), you need the update to prevent your save file from corrupting during the final chapter. SIGNALIS ROM NSP UPDATE - Switch Game