As you progress through the game, you will find Backpack armor mods. Backpack mods increase your carry weight by +20kg. Your companions can also equip armor with these mods installed. Instead of having their own inventory, companions can increase your total carry weight. Mod three suits of armor with a Backpack mod, then equip them to your character and your two companions to get a total +60kg to carry weight.
Before you find Backpack mods, you can use perks. The following four perks are recommended to increase your total carry weight:
Pack Mule (Tier 1): +50kg carrying capacity.
Traveler (Tier 1): Fast travel when encumbered.
Pack Of Pack Mules (Tier 2): +40kg carrying capacity bonus from companions.
Super Pack Mule (Tier 3): +100kg carrying capacity.