Credit where it's due, the grass is explained here:
but is conceptually pretty straightforward. I just added some additional colour randomisation, heightmap/poisson sampled the position and split it into tileable chunks that are background loaded. The chunks have LOD too so grass that's further away is bigger/more spread out, with levels of alpha dither to remove (hopefully) the seems.
Lighting is..... time-consuming. But no reflection/GIProbes here, too expensive with the Godrays plugin. I did find there was a sweet spot with the distance fog/sun effect/glow that created a volumetric look even if it's not real so reckon with enough fiddling with exposure/colour profile I could remove the Godrays and you'd only really 'notice' it missing when looking through branches, but as this was never intended to be a game I'm not too fussed. Thinking about it though you could enable area based godrays so they're 'off' most of the time.
It turns out 3D is hard lol.