I need to use a mixer/tumbler. Which one is good and has only good feedback. I've seen some have negative feedback and that they scamm..
Here's the issue with mixers: they don't work. There have been multiple studies in the past showing that through simple, automated analytics, you can still track 99%+ of the mixed inputs/outputs and tell where they ended up. Remember, BTC is pseudo-anonymous, not anonymous. All you're doing is adding in a new layer of obfuscation but anyone could break that at any time.
You definitely have a point there, but it's pretty stupid for someone to send 0.5BTC for example, and have the "clean" coins sent directly to one of his other wallets.
If you make use of a manual fee in combination with a certain delay, plus the fact that you can have that 0.5BTC sent into smaller fractions to the destination addresses, it will practically be impossible to trace them.
But yes, there is absolutely nothing that guarantees you that no one will be able to spot them. But it's giving people a safer feeling. Especially when they send the mixed coins to their cold wallets.