pretty sure the stark angled grip falls into the NFA vertical grip range.
HBI Trigger spring is a MUST HAVE ITEM you loose like 6lbs of trigger weight. Take your pick on aftermarket safeties, I like the look of the apex low profile ones, but I am currently running parker mountains. Also may want front and rear QD slots. another must have item is a paddle style mag release lever, once again plenty of choices hbi, shooters element, gearhead etc.
as for the pistol grip there are not many options at the moment, the apex is too skinny, the pakse pathfinder is too straight and the yeti is just about right being "slightly" straighter than factory but 2-3 years later still cost too damn much for what it is.
look into the Night Strike Angled grips they look like a good match, I'm running Vendetta Precision on mine: