A voucher basically banks the miles & cash for future use. But this will be tricky to use because the next time you find a suitable trip you will probably require a different number of miles and cash.

Just pay the cancellation fee and get your "taxes and fees" refunded, along with the miles of course. This leaves you free to use the miles in the future with maximum flexibility / ease.

Of course you can wait and see if the flight is cancelled, in which case you would not need to pay the fee.