Maya Unreal Nuke - Linear workflow for VFX

Hello Unreal Engine users!
I’m a look development artist with few years of experience in film and animation, and recently I’ve turned my eyes to the posibilities of real time rendering and time saving it offers (also, more and more clients ask If you can use their assets directly from the engine).
I have a few pretty important questions about linear workflow in UE, otputting render passes, setting the engine so I get absolute max samples from every aspect of it and sane not overblown values across the board.

1. Linear workflow and color space setup
UE doc says all its math happens in linear space, but conversion to sRGB happens in the code which average used don’t have any access to. This seem to create color space problems when creating render passes and rendering movie sequences. below quick example, none of the sequencer exporten images match the one I get in viewport, be it linear or srgb, colors look dull, post proces volume also does not behave identical to the viewport. Could someone explain how to properly set the sequence export? I need HDR files in exr, sRGB is a no go.

2. Render passes
Is there any kind of way to two separate diffuse, specular, sss components as separate passes? I’m not talking about raw spec or sss color in the shader input, but about what really appears in the final images. In classic rendering from arnold redshift or vray you get all components separated nice and clean which enables real flexible final image manipulation in compositing later on. Below is a short comparison what can you get from arnold and what I seem to get from UE at default. Would apreciate any kind of insight on the matter.

3. Reflection capture actor
From what I understood, real time graphics can’t sustain full real time reflections so you use refl capture actor to display reflections from cubemap/hdri on near objects in various places. There seem to be visible separation in specular and reflections in unreal (range along the surface angle, quality) as it used to be in vray, so I assume I need to use it? I can’t get it to appear in pre renderd sequence no matter what, some clarification would be mighty helpful. (please don’t point me to the doc, already read it :smiley: )

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