The DINrail device, if hooked directly to the internet router, maximizes the internet throughput because it has direct access to all three phases. I also saw a massive speed increase between devices...

The network passkey _is_ maintained through a power loss. All PLC adapters work like that. If yours doesn't, then it's probably defective.

Maximum current in the passthrough outlet is stated on the box. Check that against rated current for the device you're plugging into it.

Phase couplers are nothing to do with MIMO. MIMO uses two communication channels: live+neutral, live+ground. Your house may have multiple "live" wire phases, that's where you need the coupling (or,...

Neat, thanks! Good luck with your "home improvement"!

If you really suffer PLC signals coupling into the phone/DSL wiring, then changing PLCs won't help - they all do the same thing on the same frequency range. While disturbance of critical analog radio...