Again, "need" is not the issue here more rather, it's what you "want". The track bar and drag need NEED to be parallel to each other but, with 4" of lift, you would benefit from correcting the steep angle that they are now sitting at by installing a drag link flip AND track bar relocation bracket.
You need to install BOTH drag link flip and track bar relocation bracket at the same time. This will help keep them parallel to each other while correcting the geometry at the same time. With a drag link flip, you want to RAISE the mounting point at the axle - NOT drop it from the frame. You can do it but dropping from the frame is typically what you would do with a dropped pitman arm.
I'm not a fan of the Synergy components due to the cheap heims they use but, I understand this may be something they have or will be correcting in the future. But, being that is what you already have on order, I would just get the matching track bar relocation bracket they sell.