Usually blackout is closer to the window to avoid light leaks around the edges.

I would do the sheers against the window and the heavier drape on the outer layer, just like conventional two layer treatments.

The other option, which I have seen in hotels, is a blockout shade against the glass, sheers and then decorative panels on the top. (Three layers)

That makes so much sense, I should have thought about that.

Thank you!