I think you mean a second pistol grip or more commonly a vertical foregrip VFG. If you are making a form 1 SBR, I don't think you need any other forms.
If you are adding just a VFG and no stock, it is not an SBR. Depending on barrel length, it may or may not be a AOW.
I don't think you can make anything NFA for a $5 stamp