To maximise your XP gains, engage them solo and bring loads of bacta refills.
To maximise loot chances, bring a full squad as high level as possible, equipped with the best weapons and armour to which you have access. Scan the NPC squad to determine their weapon ranges and stay out of range of the most damaging weapons if your NPCs' weaponry allows it.
You and your NPCs should all have high dexterity for hit rating. High dodge on NPCs is good to avoid damage (but doesn't matter on you as long as you have meds, since you can't die to NPCs anyway).