The IDEfix patch itself is of no use. But IDEfix comes with CacheCDFS which is one of the best CD file systems ever.
But it is the Demo version only and comes up with nerve requesters.
You should use AmiCDFS instead, if you don't have OS3.9 (which comes with a registered version of CacheCDFS).
BTW, you don't need a file system for MakeCD. MakeCD writes CDs, the file system reads them. These functions are independent.
Bye,
Thomas