For a VM that can be started right away you need the following files:
- the vmx file
- for each virtual disk you need to have the small vmdk descriptorfile (name.vmdk - size about 500 bytes) and the associated flat.vmdk - the name of the flat.vmdk is referenced in the small descriptor vmdk)
- if the VM has snapshots you need all the vmdk descriptorfiles (name-00000*.vmdk plus the associated delta / sesparse vmdks - those names again can be looked up in the descriptor vmdk)
Files like name.nvram or the *.vswp will be recreated if they are missing.
In worst case you can recreate all eventually missing files other than the flat.vmdk and (if snapshots are used - the delta / sesparse.vmdks)
If the vmx-file is missing you can recreate it by extracting acopy from the last working vmware.log -the last working vmware.log can also be used to recreate missing vmdk descriptorfiles.
By the way - there are different opinions about the OVF/OVA export functions - IMHO that is a sunny weather tool ...
If you want full control I suggest to copy the really essential files via WinSCP