Too many games I've seen conflate being evil with being a jerk. Few games let you play the 'long game' where you are specifically nice and cooperative to deceive and manipulate. I think this partly due to decisions being made modular and point to point. Your overall morality then is calculated as some form of average of all the decisions you made. Mass effect series comes to mind.
But if you want to play as a scheming villain the opposite should be the case: you set your primary long term goal (eg taking over a country or institution) and then your actions are chosen in the vein of that goal. And those actions might in isolation actually be seen as beneficial or benign. But you ultimately do them to gain trust or deceive.
Depends a bit on alien tech level, enemy density and the map itself. In long war rebalance you get a preview of which map you'll play on before the mission starts.
Very early on 1-2 rocketeers can guarantee a victory thanks to the power of the rockets. They fall off in the mid game though. On swarming abductions I'd always bring a rocketeer because you're bound to hit something and because you're often under high pressure to immediately clear the area next to the landing zone before additional roaming pods patrol into you.