So I don't know about the little folk, but vägi does indeed mean some kind of unquantifiable strength, force, power. As an adjective (vägev), it's closest to "awesome", "mighty", "great". Yes, magical power is also vägi, but then outside of folklore and mythology, I'd dare say its meaning could be considered tangentially related to the Finnish "sisu"? As it sorta describes a person's, a group's, or even a nation's ability to make things happen in the face of hardship.
I've gone shot for shot of neat vodka with alcoholics when I was younger... And I was the one still awake after 20 or so shots. But now I can't stand the taste (I don't think I could then either - luckily the guy whose birthday it was, decided to throw all his vodka in the freezer). I don't think I've actually tried a vodka martini. I've had vermouth neat for some reason, but not a vodka martini. Given that I have half a bottle of some Ukrainian vodka I have no idea what to do with, I might go out and buy a bottle of vermouth to give that a try. Or I might combine it with orange juice later tonight because I already have some of that and I'm likely working till 5 or 6 AM (home office, software engineer, contracting, not an employee)