Constantly velocity transmission are ALWAYS in the most efficient gear. That's the only reason they ever make sense. CV transmission suck in almost every way compared to other designs.
They can however save so much in fuel that the ridiculous design and cost and problems make them still viable.
The human driver is not going to shift better than it can, it has practically unlimited gears to select from and it knows EXACTLY what the engine is doing and what the burn rate is, etc etc. The human driving simple doesn't have the information required for that level of efficiency - maybe after you jack your brain directly into the control electronics in the car.
A standard manual transmission is never running at the correct gear ratio - hopefully its in one that's closest for the task at hand, but that's the absolute best a human could possibly due - but that's unlikely because you lack the information about real time engine performance and load.
Humans aren't really that good at this sort of thing, there's just a bunch of testosterone that prevents you from admitting it.
Can a manual be more efficient than an automatic- absolutely, you can build cheap automatics that won't be as efficient as a well driven manual, but with modern tech, you'd have to pick an old design for the auto and be bad at building it before the divers is going to be big enough to matter.
Let it go. It's not 1967 anymore, environmental protection laws have required manufacturing to not produce utter shit anymore, and I do not if you heard, but they also stopped making leaded gas in the US.
You are no longer faster and more efficient than your cars electronics, you haven't been for any car built and sold in the US in the last 20 years, you're just stuck on your ego. Ok, I'm sure you can find some POS bottom of the barrel car somewhere. But the Toyota Camery has probably been better than you in every way for 20 years and it's not special at all. Something like a modern Suburu Outback with a CVT ... you won't get close in efficiency