Planar reflections notably lower performance in packaged VR project.
Linked is an example project and an example package. [Link Removed].
This was tested on a Vive Pro and Oculus Rift(not Rift S). The Oculus Rift did not exhibit this issue.
Found in 4.24.1 CL#10757647
Reproduced in 4.25 Main CL#11050671
1. Create a new blank project with no starter content.
2. Create a material(DemoMat) with:
a. Planar Reflections enabled.
b. High Quality Reflections enabled.
3. Create a blueprint(DemoBP) with a plane as a root(make it large for demonstration), child a Planar Reflection to it.
4. Assign DemoMat to the plane in DemoBP.
5. Make sure "Start in VR" is enabled in Project Settings.
6. Place DemoBP in the level, save the level (DemoLevel), and set it as the "Game Default Map" in Project Settings.
7. Remove the "AtmosphericFog" actor and the "SphereReflectionCapture"
8. Run in VR Preview. Note the stable framerate.
9. Package the project in Win64.
10. Run the packaged project.
Result: The fps is significantly lower than in Editor Preview.
Expected: The fps is stable like in Editor Preview.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-87311 in the post.