Esata speeds and options

Hi, I found this thread regarding 2008 MacPros 3,1 and have some questions about esata.

First, I believe what has been discovered in this thread is that there are two PCI slot that will support 6GBS on the 2008 MP. True? Which ones? My graphics card is in slot one.

Secondly, the Velocity Solo 2 which appears to support 6GBS on the 2008 MP will work as a bootable start up drive with a 1 TB SSD (Crucial) attached to it correct? Additionally, the Velocity has one additional plug to push 6GBS to an external drive via esata cable. Correct?

Finally, my current config is that I have the SSD in the standard MP internal hard drive bays. Am I limiting the speed of this SSD by having it in those bays and would I benefit from the Velocity Solo config? How much faster is the Velocity/SSD over the standard 4 bay bus in the MP?

OS El Capitan 10.11.6 (15G18013). Below shows a Newer esata card for "hidden" esata ports on MP, reportedly 3GBS bus shows 1.5GBS speed for unknown reasons. Graphic from Apple System Report. Comments? Thanks, Russ