Erdo4
Need more info, what jagged shadow and what flickering? It's probably better to post a new thread in the Support section.

Oh, that. Not much you can do other than decrease the shadow update frequency by adding something like this in Skyrim.ini under [Display]:
Up close the shadows will always be somewhat blocky no matter you do.

@ Erdo4

I noticed you also wondered what depth bias did to the shadows on that youtube comment thread. Lower values will possibly make your shadows sharper and more defined, but it will also increase the appearance of the famous shadow striping bug. I use 4096 shadow resolution for 2 of the 3 shadow resolution settings the 3rd one (iShadowMapResolutionSecondary) i use 2048 resolution. With those resolutions I had to set the fShadowBiasScale to 0.2 to get rid of the exterior shadow striping. But also to note if you are running low enough fShadowDistance those exterior shadow stripes won't render. I haven't tried it out myself so don't know at which distance the possible shadow stripes will disappear but if I would guess it would probably be somewhere around 2500-3000 I think.

Also if you however set it to high small shadow parts will disappear, for an example leaves from a bush will have less shadows with a high depthbias then a low depthbias.

Almost every tweak guide recommends 0.16 but very few explain why they do it!