Okay so to go over it since you said you do not wish to use anything that was left on it.
So if you've already uninstalled cbhc from homebrew launcher, you can go ahead and uninstall cbhc, haxchi, wup installer and the homebrew launcher from data management.
As well as delete the other users. But like I asked I want to confirm you can perform every regular task from your own created account before hand.
Because there's no such thing as cfw that prevents online access, so not being able to update is a red flag.
I'm suggesting because its important. Try to update Xenoblade, and play Monster Hunter online from your own account.
If you can then you no longer need anything from the previous owner. If you cannot you are going to want to keep some of what is on the SD or USB with the homebrew (not the channels or users) to make it easier on you if fixes need to be made.
Ok i try xenoblade and when i get my monster hunter 3 then i try to play online. If it's work then i delete everything. If not then i am gonna write here again.