The issue with light shadows is fairly rare, and QA was unable to reproduce it. Without much to go on, the programmer looking into that said it was likely a driver issue.
For the portrait, did you try starting a new game after disabling light shadows? Did you try other characters?
Try verifying local files: in the Steam library, right click on the game and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
With the GOG version, in the (optional) Galaxy client, select Divinity: Original Sin 2 in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'.
