I’ve played for a while disregarding battlepacks. What I would like to know is, if I should just open them all up?
Additional questions:
Do I spend the XP boost immediatly after opening the battlepack?
1A. Do they stack?
Do the weapon attachments only fit onto 1 weapon of choice, or would I be able to put them on all weapons?
*Edit: thanks guys 
I’ll activate right away
You activate boosts. Go ahead and open them. They have equipment unlocks for weapons that you could end up finding useful. They are only per weapon though.
If you don’t use em than what’s the point of getting them? Open them up and use the XP boosts buddy!
There is no disadvantage to opening the Battlepack. Boosts are not activated until you choose to do so. They do not stack. Weapon mods are unique per weapon, so each battlepack mod unlock only applies to a single weapon.
They do stack. I have 6 %25 4 %50 and 2 %100. This is PC though.
Stacking means using more than one at a time and having the effects of both “stack”