Officially you can't augment with both an Affinity and a Feat under that Affinity - or even with two feats from the same Affinity (because that's using the same ability twice). I understand that that makes "augment-only" feats rather useless unless they have some other advantage.
In the case of "Sword-help" I'd allow it to directly augment someone else using a sword. Another possibility is that there might be cases where the Feat is more appropriate than the Affinity.