Cloning the objects into workspace won’t be more lag. If you’re concerned about the boss constantly spawning parts and dealing special attacks, then check out PartCache:
PartCache works by keeping a cache of parts already in your workspace but really far away where no-one could see them. Every time you need it, it just changes the part’s CFrame to teleport it to where you want and when you’re finished with it, you can reuse the part and teleport it back. If you ever run out of parts in the cache, then it will create new parts as necessary. Setting the CFrame is the least expensive way because putting anything in workspace would require the game to update the physics of each part.