First: Is there a way to tell Cycles to render only a reflection/refraction pass ? With no diffuse, etc. ?
Second: Would this be doable in such a way that there would be a panel in the EEVEE settings and it would say: Cycles Reflections/Refraction ON, Render Precision: 0,25,… etc…
This would only mean one thing: Render the reflection/refraction passes at a lower or same res, and send it to the buffer of EEVEE.