Did some performance testing, in the highest shadow area in the jungle in the beginning of the game, the larger r_shadowatlastilesize values get very expensive, very quickly. In the indoor parts it's a lot more reasonable though:
r_shadowatlastilesize 2048 (highest you get with the highest setting in the settings menu): 6.0ms frame time
r_shadowatlastilesize 4096 (my recommended): 7.1ms
r_shadowatlastilesize 8192 (beautiful, but spendy): 10.5ms
And to sum up my current recommended options for prettying up the game:
r_shadowatlasheight 32768
r_shadowatlastilesize 8192
r_shadowatlaswidth 32768
r_shadowsfadedistancemultiplier 5
r_shadowcachehalfprecision 0
r_lodforce 0 or r_lodscale 5 (note in my previous post, I mentioned r_lodforce 1, but that's not the best LOD, 0 is the highest quality one, so far as I can tell. The desk in the office just before the first fight is one of the best spots to change LODs on the fly and see the results.)
is_poolSize "8192" (this is the texture streaming pool size, I believe, and you'd only want to set it this high on a 24gb card, default on my 3090 with max settings was only 4600MB)
While playing around with the r_shadowatlastilesize setting I noticed in some scenes I'd see warnings in the console saying 'too many shadow slices in view' and visibly broken/missing shadows, while I had it set to 8192.
Turning it down to 4096 fixed the issue, but so did incresing the r_shadowatlaswidth and r_shadowatlasheight from 16834 each to 32768 each. Doing so increased VRAM usage from 13450MB to 16522MB (at 720p internal resolution!) though, so you burn another 2GB of VRAM on shadows alone.
Kind of like the texture streaming pool size, if you've got a 24GB card, might as well put it to use.