So my initial thoughts when you guys were talking about all this ethanol free stuff was you are splitting hairs, I have never had a problem using 10% ethanol, I kind of like it sometimes because I feel like it helps clean stuff being in there. (If you've ever seen the inside of a race engine on methanol, you'll know what I mean). However, pure methanol does not lubricate anything, in fact it washes everything dry, so wear tends to increase. Mostly gas with a little ethanol I feel like is a good compromise. With that said, it is more susceptible to sitting or separation over time or if water gets in the fuel(this can cause separation), but I never recommend leaving a fuel tank sit for longer than 6 months for one winter, and when I do, I make sure its mostly full, it's worse to leave it sit almost empty. I don't recommend this with or without ethanol added.
On the fuel mileage, IF the PF4 is self correcting A/F ratio, it is possible you may see a slight improvement, because gasoline stoichiometric is about 14.7:1, and ethanol stoich is about 9:1.(Methanol is 6.4) During WOT you run richer than this, but during cruise or low load its not uncommon to be close to stoich. That means pure ethanol would use approximately 40% more fuel for the same air. So if you have 10% ethanol in your gas, 10% of 40%, you potentially would use 4% more fuel IF the engine is correcting for this. If it is not, you should not see a difference. Sometimes on long trips I look at the lbs/hr on my EFI, but I haven't done that in years. It's kind of like the instantaneous fuel flow at any given highway speed, etc.
However, since typically ethanol added gas is a little lower cost than pure gasoline, I don't think anyone would see a cost savings by running pure gasoline and potentially saving 4% more gas (possibly not because the engine has to correct for this, although many modern engines do). Usually the price difference is more than 4% though, so cost savings is possibly cheaper per mile with the ethanol?
When it comes to octane, you guys are correct, higher octane generally has a higher resistance to detonation, but a slightly lower energy per gallon. Usually this is negligible. I buy the octane my engine needs, regardless of 10% ethanol or not. An engine that has high compression may need 91 or 93 to not detonate or ping, etc. In that case if you use 87 it may cause engine damage and you may lose power. However, a, engine with only 9:1 compression and a low dynamic compression doesn't need 93 octane, and running it is kind of a waste of money. That 9:1 engine is going to make the most power at a certain ignition timing, and above that timing it won't make more power. So putting in premium fuel and more timing won't help you. Theoretically it will have lower energy, but I'm not sure you could measure it.
Now that I have said my opinion, maybe I should watch the video you mentioned above, it might be interesting.
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