MimbleWimble is actually similar to Monero in the fact that both amounts and addresses are not visible at all. Even Fluffys project Tari uses MimbleWimble.
MimbleWimbles spend privacy is even worse than Monero though because they don't even have ring signatures. So you 100% know someone made a spend (but still not how much or to whom). But a good thing about MW is that if the data is not collected at the time the transaction occurs that data is gone forever.
DarkFi is definitely interesting I just don't know that much about it. I know Amir Taaki is involved and that it is merge mining with Monero now.
Here is a chart to visualize privacy leaks with different tech VS scalability:
MWCS = MimbleWimble + CoinSwap
CoinSwap is not implemented yet on any MW protocol afaik
