The "more reach" option is ticked. I thought large power poles should have more reach than substations?

Oof, that's a bug. In my code I have:

    ["substation"] = {
        ...
        wire_distance_override = 34, -- vanilla reach is 30
    },
    ["big-electric-pole"] = {
        ...
        wire_distance_override = 20, -- vanilla is 18
    },

It should be the other way around :/

I'll have to think if I'll fix it, because it will break many setups.
but the vanilla reach is actually 18

Can you at least increase large power pole reach?

That won't break anything, so it should be safe

True. Fixed in the newest version. When I opened my test save I vaguely remembered last time I made big changes to the mod my high-voltage transmission lines in my test-save was acting weird. I just assumed that it was because the test-save is so old, but turns out it was because the wire reach was wrong. Thanks for pointing it out!

A bit off topic, my apologies.
Why no startup options to alter the wire length and supply areas? Seems like a natural thing to include, so I figure there is a reason.

Also, does it cause complications to connect poles with a copper wire? Do copper wires perform any function?
I ask, because there are some mod tools that rely on a existing copper wire connections.

Why no startup options to alter the wire length and supply areas? Seems like a natural thing to include, so I figure there is a reason.

Personally I like keeping settings to a minimum. The more settings, the more things I need to test and the more maintenance and complexity in the code. But it should be possible to change these parameters using other mods, as I discussed with you here :).

Also, does it cause complications to connect poles with a copper wire? Do copper wires perform any function?

Yeah, unfortunately as soon as two poles connect with copper then they share a network, which will break the way this mod works. When I rework this mod I will try to hack it in, because copper just looks so much nicer than the overlay I draw. But it will not work with tools that expect a copper connection.