I want to add to dot's point that when Nietzsche talks about power I think he usually says "macht." This could be rendered as "might" but I think with Nietzsche that would be misleading.
The intention might be clearer if you were to render "macht" as capacity, potentiality, or something along these lines, because his sense of it usually seems to be a Spinozist one, where what increases your "power" is what increases your capacity for affecting and being affected.
I.e., my sense is that he's really never talking about the kind of power that would be manifested by muscles, machine guns, barbed wire, cash reserves, and so forth. And if I recall correctly he's pretty clear that the accumulation of these things is really a dead end.
It could be true that there is still something economistic about this line of thinking–If by economistic you don't mean an economy of money, but something like a "general economy."
And, in a certain way, you could argue that this is still a kind of imperialism, but I think you would have to grant that it's a very strange kind, where your struggle against your surroundings might well take the form of, like, going for a walk and admiring some geological formations, attempting to treat your various illnesses, engaging in urbane chitchat, taking all your belongings with you and moving to a different furnished room all the time to get the right weather, etc., etc.