I can say from direct experience doing research with hollow-core fibres that they are not easy to splice either to each other or to standard fibre. Imagine trying to use heat to melt together a pipe and a solid cylinder without creating a mess.
Tor is way more secure and anonymous of course, but not at all practical for high bandwidth / low latency applications. Yes you need to trust the VPN that they don't log (your points 1-3). If you trust them not to log, then there is nothing they can reveal under court order (your point 4). It's not snake oil if it does what the seller says it does.
The performance of my network is certainly not terrible when connected to the VPN. Download speed is not noticeably affected and my ping to quake servers (I run VPN all the time, even while gaming) is often lower with the VPN connected.
Regarding your 'why is it more secure' question - because I live in the UK where the government and a myriad of its approved bodies are now allowed to look at user traffic and see my IP and what websites I've visited. I don't have to worry about that now - although yes I need to trust that PIA really are not logging.
I could be on the wrong track here, but the MACE ad-blocker built into the PIA VPN seems to work very well by itself. It's not free like PiHole is, but pretty cheap, and a VPN is probably a better starting point for security than a local blocker. Am I missing something here?