So if i would like to withdraw funds from chipmixer it'll the best if:
1. Export the private key from chipmixer to wallet --> Disconnect the Transition from the Blockchain
There is no point to step 1.
If anything, all you are doing by "importing" your private key into a wallet, is increasing the chances that your funds might get stolen... due to exposing the private key (ie. having to type or copy/paste it into a potentially compromised computer) and leaving the funds sitting on that key for a period of time. Granted, given proper precautions are taken, the likelihood of that is relatively low, but still... it is an unnecessary step.
It doesn't really "disconnect the transition from the blockchain"... as there is no "transition". The funds remain on the same address (as controlled by the private key) as already recorded on the blockchain.
2. Sweep the funds from the private key which had epxort in your wallet from step 1 in an other wallet --> Diesconnects the funds form chipmixer due to private key exchange.
So my assumption that this is the best way cause the first step disconnects your from the blockchain and the second one from chipmixer.
Even if the last step connects you with the blockchain again you are not linked with chipmixer anymore in this transition.
If by disconnect, you mean that it removes the chance for ChipMixer to "go rogue" and steal your coins... then yes... your funds are now "disconnected" from ChipMixer.
However, as the blockchain is a permanent, public record, it will more than likely be possible to show that the funds originally came from an address that was more than likely related to ChipMixer... so the funds can probably be traced back to ChipMixer, so technically, they're likely to stay forever "linked" with ChipMixer.
In short... just "sweep" the key... this means you only "expose" the private key once and can then discard it.