There are ways to tweak it, but unfortunately most of the scalability settings do require HWRT. FOR SWRT, you can increase the distance field voxel density to get better resolution, as thin geometry tends to be a problem. Scaling up the mesh means a lower-rest voxel grid is taking up more and more world-space volume, which often results in light-leaking. If you have visualization screenshots I might be able to understand better.
And ignoring distance field lighting may be acceptable, I also know there are ways of having something stop casting lighting but still receive it, not to mention SSGI and SSDO will still work, so you’ll never be completely without GI coverage.