Does the AI just target the player character or does it prioritize whoever is dealing the most damage?

I made sure to play the campaign tutorial but ultimately want to have my own little story going on. I'm pretty new to this universe with pretty basic knowledge on the houses. Should I still start with Campaign? I imagine there's some tutorialization I have yet to experience, but I'm curious if things are overwhelming enough to prevent me from understanding what I'm doing if I just jump into career. The only real experience I have with anything remotely close to this is the first mechassault on the OG Xbox...

Is there a mod that adds and extra lance to accompany me during missions? Like that I can deploy.. I haven't found any an if it exist maybe it's worded differently.

Now that there are clan mech assets from the new game, seems like it would be easy to create a clan invasion DLC for MW5 yea? It would make for an amazing end game crisis and "final boss" if implemented well.

I read that the quality of life upgrades mod adds in more detailed mech info like proper DPS etc like YAML has but I was only able to find "Quality of life upgrades 2" which adds Thermal Vision, Headlights, Godmode, FPS Limiter, Mech loadout save/load & Starmap search. Where can I find the one that adds the detailed info without having to use YAML coz I feel YAML makes the game more complicated than I want it to be....