In D&D I absolutely hate Lawful Good characters because they are REALLY inflexable. It makes it a drag, cannot steal or do anything to forward your cause without some snarky whiney lecture. The "evil" route would be to kill EVERYTHING and nick all their shit. You would have figured a way to kill the Druids and Tieflings probably by setting up BOTH sides for heavy losses then killing the leftovers. Evil characters are out for themselves, tadpole or no. The second an "evil" character figured out they cannot get help off either party the gloves would have come off OR they would just move on if they couldn't be arsed.
There is no "evil route". If you pick "the path of least resistance" that makes you smart/lazy not evil.
I agree with you about hating Lawful Good Sometimes what they do I consider evil.
I do not think you are seeing evil as anything other than Chaotic Evil however. Sometimes evil will do good things to gain benefits, sometimes they just simply don't care. Sometimes it is even better to keep people alive, most of the time someone with nothing left to lose is much more dangerous than someone with hope who you can keep in line. There are many other things an intelligent evil character would do before murdering everyone (ofc this is also an acceptable route, just pointless.) Not sure what you mean with "path of least resistance."