Issues with Mods
Due to the nature and number of changes in major game updates, there are invariably some mods designed for previous game versions which will cause conflicts and problems after an update. This is possible after hotfixes, but much less likely.
In the past, problems have included startup crashes, crashes or missing options/models/textures in character creation, characters being encumbered at the start of a new game, being unable to exit the game options, being unable to leave camp, and cosmetic issues such as Shadowheart's hair being given a metallic texture.
If you have any problems with the game and have mods installed which were not specifically designed for patch 8, or confirmed to be compatible by the mod author or community, try removing them.
Check the 'Mods' and 'Public' folders in the '..\SteamApps\common\Baldurs Gate 3\Data' folder, etc; if present, both folders are safe to delete). If applicable, you can also delete the modsettings.lsx file in the profile folder, if you're not using a new profile for patch 8.
Starting with patch 7, the game uses the local AppData folder for the current user account: 'C:\Users\<UserName>\AppData\Local\Larian Studios\Baldur's Gate 3'.
For compatibility, if there is no local AppData folder for the game when it is started, but there is a game folder in My Documents, it will copy the profiles and configuration files over from the Documents folder, but that may mean copying old mods there, as well. If you didn't already check this, the easiest way to get to that folder would be to copy %LocalAppData%\Larian Studios\Baldur's Gate 3\Mods into the location bar in Explorer and hit Enter.
If the launcher is not giving a data mismatch warning (see above), that should mean there are no mod files in the install folder or the Mods folder.