There are situations where you’ll have to fight, like infiltrations, as a result of certain projects being in progress or defending your stuff against anti-AI warriors if you’ve been too agressive.
If you don’t go around choosing project options that will bring you in conflict with humans and appear hostile it’ll generally stay more quiet. It’s not like the game tells you explicitly what will happen, but I think you can guess that Commercial VR pods will cause less of a disturbance than the Torment Nexus route where your workers actively capture humans.

It’ll be a while before you’re forced to confront mechs when you play the tutorial. They’re pretty easy to deal with if you have a Raven to hack them. You can’t control captured mechs or bulk units (another unit type) directly, but they’re useful later on if you’re in big fights as they fight enemies during the NPC turn without you needing to spend mental energy.
Other than that the mechs are just a more tanky, longer range and mostly harder hitting type. When you capture a new mech type you also unlock its corresponding altered version you can control more directly like your normal androids.

Combat in general takes place on the same map and using the same mental energy you need to move your androids around. Just get your androids into range (light blue circle) and click the enemy. There’s a bunch of modifiers to get advantage from behind/above or light enemies on fire, but it’s not really necessary at the normal difficulty imo.