I dont really know how much certainty the above articles provide, but it casts some doubt as to exactly how far the anonymity goes. At least if its what I was after, Id keep reading these sort of articles for a few days to get a better idea of the extent.
May be the articles are true or may not be.
As per theymos, 100% anonymity isn't possible. Moreover, I have read a thread here where an user have showed breaking some of the mixing site.
I don't know much about MimbleWimble, if I am correct it's something which remove data from the blockchain which can ensure anonymity. I will not surprise if they have flaws because Monero as well have flaws which I have read a while back.
I would follow the theymos guideline which is the maximum level of anonymous transaction at the moment.