Do I need to deploy token and crowdsale contracts from different accounts in MetaMask and do I need a third account to send proceeds to if successful?
No, you don't have to. It's design specific, you can achieve your goals either ways.
In my personal opinion, there is a benefit of having a separate contract address for different purposes- design-wise.
It offers a clear mental picture for the deployer(s) in terms of specific functions.
Another benefit is that certain actions could be divided between two parties (say token sale pre-crowdsale, and actual crowdsale). Now different divisions could deal with different tasks.
The other benefit is the ease with housekeeping. If we have to watch which transactions are made by whom, it's much easier to separate the transactions on the basis of the different addresses you used.