RAM is one of your least power hungry components compared to other parts of your computer, such as what generates heat (CPU/GPU) or produces physical motion (fans or spinning drives).
This makes no sense. RAM generates heat just as CPU does, and RAM also actually does consume a substantial percentage of laptop power. However, said usage isn't related to how much RAM is being used, really; it's a constant usage rate to keep the current RAM state alive.
Well, it makes sense to me: CPU and GPU take in the order of 10 times as much power as RAM. RAM power usage just isn't depending on load, like that of CPU and graphics.
Reducing RAM usage will reduce disk activity, though, so there's that.
Why would that be? Unless you're frequently running out of RAM and swapping to disk, RAM usage shouldn't correlate to disk usage much, right?
Because all of that "unused" RAM in the background is actually being used by the OS for disk caching, thus reducing the overall frequency of reads.
No, if anything the energy impact looks worse than before on OS X. I love Chrome, but the fact that it's almost completely unusable on laptops that aren't plugged in is problematic.
Hard to know. Lower memory usage will generally help battery usage, but it sounds like the garbage collection is more aggressive now, which might offset the savings.