depend on the enemy faction and the difficulty, but generally the necrophages is the only one that does this but they are also the insect swarm faction.

What Lorco said. Just chiming in to say EL isn't RTS but TBS :)

If you choose a low difficulty, the game will be very chill, dont worry. Also its a simultaneous turn based game, so there is no "stress" per se.

For maximum chill you can play against only Roving Clans factions. They can't declare war against you.

They may attack you with mercenaries on middle/late game, but I have never seen the AI doing this...