I’m happy to help if I can 
. I agree with you, DFAO +SSR/SSGI dosen’t have a comparable amount of quality to lumen, to the point where the SSGI documentation recommends only using it with other systems like baked lighting. SSGI has some quality settings that help to reduce light leaking and enhance accuracy, but there’s no fundamental solution for the view-dependent problem. And you are entirely correct, even though Lumen looks quite similar to the path tracer on high quality settings, art direction tends to be different between baked and dynamic lighting.
While duplicate levels are an option, what I would recommend stronger would be the data layers system, which lets you swap out large data sets, meshes, and even game logic in-and-out of the same persistent world, as requiring dynamic networking between two separate levels based on hardware type sounds like a nightmare to implement.
If I may ask, what do you mean precisely by ‘minimalist’? If by that you mean a closed, relatively static map, then lightmass should work pretty well, especially with Distance field indirect shadows and SSGI to stop dynamic objects from sticking out. If you simply mean simple in geometric and material sense, and leaning on lighting to do the visual heavy lifting, then your art direction may have some fundamental implications for what path you wish to choose, static or dynamic .