Yep, the shadow quality in Horizon is pretty impressive overall, especially for an open world game. The only drawback is the relatively low shadow range. In the village of Meridian, this can be especially noticeable, but generally a non issue. Shadows are drawn much further than FFXV, at least. As for ND, the improvement I want to see in TLOU2 over UC4 is definitely shadow quality, which was a low point for the latter.
It's generally good in the open world. It's just in the Meridian village that shadow pop in was quite noticeable for me. Then again, I'm on base PS4 and the Pro version supposedly has greater draw distances, so that could explain it.
Probably not, there aren't the light bounces and color bleeding typically associated with global illumination. Most indoors also lack any sort of GI, it seems, the lighting can look flat at times. Not sure about Cauldrons and ruins, though. The indirect lighting looks much better in these places.
UC4 didn't have GI. It had a number of situations that implemented localised fakes (underwater flashlight scene) but it wasn't a universal lighting solution. It had baked lighting and occlusion drawing (shadows) that wasn't implemented in some places.
While it didn't have global solution, it did have a light bounce for flaslight using reflection shadowmap and 64k virtual pointlights.
) And I also forgot the letterbox 
