This may look trivial but...

[Chickensoup23]

I haven't found that anywhere (including stickies). It's a super stupid question but...

Which folder do I delete to delete all my current user interface and its settings? I know a new one will be created once I re-enter the game, but I'm just wondering which ones are the ones to delete.

Thank you,
Chicken

[Chrysia]

In your WoW folder is a subfolder called Interface, that would be the one. Alternatively, if you're just trying to get rid of add-ons, there's a subfolder in Interface called Add-ons.

[Jaco]

I haven't found that anywhere (including stickies). It's a super stupid question but...

Which folder do I delete to delete all my current user interface and its settings? I know a new one will be created once I re-enter the game, but I'm just wondering which ones are the ones to delete.

Thank you,
Chicken

Pretty sure the WTF folder.

[Jadè]

Deleting Interface will remove all addons.
Deleting WTF will remove all UI settings.

[Aciied]

You delete your addons in the Interface folder, and you delete your settings (also addon settings) in the WTF folder.

[Chickensoup23]

Thanks all, answered all my questions!

WTF = Settings
Interface = Add-ons, the physical thing. (And other WoW stuff)
Cache = something that I don't know, BUT

All this should, imo, get stickied somewhere, or added in in a thread. I'm pretty sure everyone used that/wanted to know that one day. These 3 folders are the 3 folders I hear the most in WoW. They're important, imo.

[ComputerNerd]

The Inferface folder may contain your addons but the "Saved Variables", their settings or configuration are saved in the WTF folder.
Certainly as far as reverting back to the default UI, blizzard themselves suggest deleting those 3 folders, though depending on the issue, if you are just troubleshooting then renaming the WTF and Interface folders to something else will suffice should you later wish to restore them, or at least not lose something in them.