Uh these effects are super amazing, if you look at your stats, each little bubble tells you what they do... You need the +1 to reach a full bar of the stat that your character prioritizes

Well those automatically get put in as you level, but you can add the effects from the alloys or others by crafting it into your character, but you can only do one per character

one per costume....but yea basically they dont stack. can only use one man so choose wisely. u can add a different one but it takes away the current one