Ok great so a 2.x/16/256 15" with Iris 6200 would have no bottlenecks?
Even with maxed out (or almost maxed out) CPU?
Every computer has bottlenecks i.e. performance limitations. Or do you mean something else? Nothing about your proposed configuration would be so constraining as to prevent other limits from being reached. Apple have sold millions of MBPs with 2.x GHz, 16GB of DRAM, and 256GB of SSD (not yet with Iris Pro 6200 of course).