It's not voltage, it's continuity. (Though you can also check the voltage between them first if you feel like overdoing it, it should be zero or *very* close to it)
And this wiring really doesn't look all *that* old to me. The only thing that's different to the modern stuff I know is the aluminum earth wire. In comparison, my parents' place has some of the first commercial armored cable ever made, which is also the only reason it still has most of the original wiring... (It's the same wires as knob-and-tube, but inside a fairly sturdy *steel* jacket. Which both pins the insulation in place and provides a "not terrible" earth path. I have to cut the stuff with a *hacksaw* whenever I'm tearing chunks of it out)
EDIT: And also check that the type of wago connectors you have are listed for use with aluminum wire, since not all of them are fine with it. (It should also say whether or not it requires the paste, but it never *hurts* to use it)