For instance, I only want lit substations and large power poles, not the small or medium ones, and I don't want the small/medium ones to show up in my game.

I've tried moving two of the entries from the whitelist to the blacklist but it didn't seem to work. I added the mod to a save that started without it.

You just need to add
small-electric-pole
medium-electric-pole
to the blacklist and load game without synchronization
That way all lighted small and medium poles will be destroyed and won't be visible in your game

Very nice, thanks.