The modpack contains mods that rely on most of the DLC, so if any one of them is missing, it'll give exception report so please make sure you have all of them installed (YES, ALL OF THEM) otherwise you would get multiple exception reports and glitchy UI, and you wont be able to play the game. You can use Anadius Updater and Unlocker to download and unlock them if you dont have it (Link)

Onedrive is often the leading cause for Mods conflict since it restores deleted files and packages so it's necessary that you disable it for Mods folder. Here's how.

You can add your own CC in a different folder (like "16 My CAS") but keep the rest of the folders untouched since Update Patch (used to update your previous Modpack ver.) requires the folder layout to be consistent (dont change any of the folder names shown in above pic, otherwise the patch wont work).

Adding CAS packages (like outfits, dresses, shoes, skin details, etc.) is completely fine but same thing cant be said about scripts and mods, since I dont know what effect it can have on other mods and gameplay, and potentially, can cause conflict and create issues. So add them at your own risk and I wont be held responsible if any issues arise from it.