Disclaimer: I'm not an expert on this, so be careful. No warranty.

I think the worst that will happen is that nothing occurs if you connect it to a PiJuice reserved pin. You can try it, but it probably just won't work.

Fortunately, you probably don't need to. There's a lot of ports that provide power, and according to this if you want 3.3v connect it to pin 17. I'm pretty sure I've got the same EPD as you, so if you have a look at my cables in the building a prompt section, you can see that I've not got anything on GPIO 1, I think I remember moving it to pin 17.

As far as I can tell the dangerous things you can do when plugging things in to the pins is

* Plugging a cable to a pin providing voltage that doesn't want voltage

* Plugging a cable that goes to ground to a pin that isn't ground

So as long as you're careful and only utilise pins for their assigned use, you should be right.

Otherwise, if in doubt check the manuals.