Performance LUN sizes Oracle VMAX

We are looking to move Oracle DBs to our vBlock that has a VMAX on the backend.

My main question here is to see how the storage is laid out and what size LUNs to used to avoid the vSphere limitation of 256 devices.

It’s also my believe that the size of the LUN doesn't really determine performance but LUN to DISK layout determines the performance.... any thoughts?

Is there really a common design to say always use VMDKs or RDMs or is a mixture the best way.

     To me I think mixed is better, based on the layout of the VMs and their sizes.

I am thinking 500GB LUNs as a standard.... or maybe large.. but need some test results if possible.

Let me know if you need anymore information...thanks in advance