I haven't seen Bill answer this one so I'll try and reply to Bob's questions since I can't remember if he asked Bill these at the meeting.
Ooh! Hey, Bill; how do they tie in, or do they?
Not sure what you're asking here, Bob. If you mean the article and Bill's presentation. The article mentions Opera's VPN client and Bill was doing a presentation on Opera.
Does PIA make the VPN plugin(?) redundant, do they conflict, do they collaborate to enhance protections or open additional functionalities?
If you get PIA, you don't need to use the VPN plugin in Opera as they both provide VPN services. The VPN plugin in Opera will only provide a VPN for browser connections through Opera though, so if you need VPN encryption for other Internet-connected apps, you should use PIA or another service that provides a VPN client for the entire OS. I just tried using Opera in Linux with the VPN turned on and my PIA VPN client also on (it's always on except for Netflix) and it works fine. Of course, there will be an extra overhead to using both. A VPN inside a VPN! Even for me, I think that's overkill!
Note that Opera's VPN servers are possibly slower than commercial VPNs. These are speed tests done before and after turning on their VPN:
Before:

After:

PIA's VPN servers are fast. Some have been slow occasionally but have done lots of testing and usually, they're up with my normal network speed. And to be fair, I did a speed test before this with the VPN on and it showed 22 Mbps. But unless you're doing downloading, you're not going to notice the difference between 16/22 Mbps and 35 Mbps while surfing the web and can even stream Ultra HD videos over it which is just enough for 7.0 GB/hour if my calculations are correct.