There's a lot of threads for this. However to answer your question, keep it stock until break in of the orings (20-30,000) shots. There you can lower the dwell. I have a Pooty polished geo bolt and run 10.5ms. I've gone down to as low as 9ms but I noticed some inconsistency and a little drop off. I also have a non polished bolt and run 11.5ms.
As far as efficiency I can get 8-9 pods and a hopper on a full fill. Your not going to get the 9+ pods consistently on this gun.
As far as the updates from the geo 2. No performance updates have been made. The only internal difference is the location of the purge on the 2.1 and the POPS ASA, which you can buy.