I got a fresh computer but I can't delete my resource packs. This thread is the cloest I have to a resonable awnser. Although I can download, enable and disable the packs, I can't see them in the folder, that's why I can't uninstall them.
I've checked all the users on the pc and still no luck, maybe it's because I am using terraria on a family shared library, so maybe the resource pack files are stored in the steam cloud for me, but the players and worlds aren't synced. Well time to uninstall terraria.
Edit/Solution: I didn't think of it, but by unsubcribing from the steam workshop page, it gets removed. I still don't know where tho.