In case of Bitcoin, it is 10 min.
What is the case for ETH or ERC20 based token? And what's the confirmation time change after Casper update?
An ERC20 token is just an Ethereum smart contract. Any operation with tokens is a transaction which must be confirmed by the Ethereum network, just as any other transaction. Assuming that the fee is sufficient and the network is not overloaded (which sometimes happens during large ICOs), transactions are confirmed within a minute (an average block time at time of writing is ~24 seconds).