Blueboy84, Yes, you can use 2 X 16GB Memory under the optimizer mode.  By populating memory banks A1 & A2 (recommended) on separate channels you achieve supported speed of up to 1333 MHz as opposed to speed of 1066MHz when you use A1 &A4 banks. For future memory expansion I recommend you use the Single Rank DIMMs or Dual RankDIMMs as opposed to Quad Rank DIMMs. Quad Rank DIMMS use only two of the available banks in the channel.
We have a Dell PowerEdge T710 server with only 1 processor and we are looking at installing 2 x 16GB of RAM. The server is set to optimizer mode. With this configuration can we install only the 2 sticks of RAM or will we need to buy a third?
Dell PowerEdge T710 Memory Configuration with 1 Processor