1. They are the same amplifier, but only the difference is the primary input connector being either RCA or XLR. (XLR amps are not currently available with no timeframe on future availability)
2. The F-hole is simply a cut out on the amplifier like you would see on a violin or cello, it's just a decorative option

3. The Neutrik connector allows you to be able to disconnect the amplifier from the woofers using single connectors. It has no bearing on performance
4. There is no audible difference in performance. The dual opposing option is slightly shorter, and a little more physically balanced since the eight is distributed more evenly.
most people choose the dual forward for looks more than anything.