I just use your free version of UB Data Migration module, and I get some issues on the configurable products.
They are exported with a attribute set that does not have the configurable products options.
On your PRO UB Data Migration this issue is solved?
Both our UB Data Migration Lite and UB Data Migration pro supports to migrate configurable products. As we could not reproduce the issue you mentioned, if you can provide us with more details, we will check further.
Anyway, I highly recommend you consider our Pro version, as you have full package of features to port not just products to M2. Meanwhile, it is fully compatible with Magento 2.1 and support Nginx (in case you use Nginx server).