Are there withdrawal minimums and fees?

Yes, each asset has a minimum withdrawal amount associated with it. You can find the the corresponding minimum withdrawal amount through this link and inputting the asset you would like to check: 

In this case, you can see that the "min_withdrawal_amount":0.0001. This means that the minimum withdrawal amount for BTC is 0.0001. 

The letters in the URL (in uppercase) after “/currencies” can be changed to any Exchange supported asset you would like to check. For example, the corresponding link to check the minimum withdrawal amount for ETH would be: 

Network Transaction Fees

For transactions on cryptocurrency networks (i.e., transfers of cryptocurrency off the Coinbase platform), Coinbase incurs and pays network transaction fees (e.g., miner's fees). When you send cryptocurrency from your Coinbase wallet to another wallet, we will charge a fee based on our estimate of the prevailing network fees. However, the final fee that Coinbase pays may differ from the estimated fee due to factors such as batching transactions or changes in network congestion levels. All fees are disclosed at the time of the transaction.

Efficiency Gains and Network Fees

Due to potential efficiency gains from batching transactions, the aggregate amount of estimated network fees paid by users within a given batch may exceed the final network fee paid by Coinbase.