None of these ported subs are immune to port chuffing. The VTF-2 is no more likely to chuff than any of the others mentioned in this thread. And if you really want to stay away from chuffing, use all ports open on any variable tuned subwoofer. As for the PB1000, there really isn't a good set of measurements out there. I would guess you can take the PB2000 measurements and subtract 3 dB from them, and that will be its ball park performance, maybe. You can ask SVS, they may not tell you the exact numbers, but they probably will give you ball park comparisons with their other products.
As for 1 meter vs 2 meters, those measurements can be equally converted. As distance is halved, so is amplitude, so subtract 6 dB to go from 1 meter to 2 meters. Conversely, add 6 dB to go from 2 meters to one meter. You have to also keep in mind RMS vs peak output. Most testers who do 2 meter testing use RMS. Most testers who report data at 1 meter use peak. The difference is 3 dB, so any measurements you see reported in peak, just subtract 3 dB to make them comparable to RMS measurements.