I would agree with most everything others have said except in the case of the Swashbuckler. I would like to see the off-hand attack adding the damage bonus because, really, that particular archetype is made for dual wielding and it should be built into that subclass. However, taking two levels of fighter isn't a bad way to really spice up that character. Dual wielding isn't that much of a boost to fighter-types, since once they get two attacks the one bonus attack doesn't help them all that much. Other fighting styles and feats are much more effective throughout every level for them. I am enjoying playing my Tabaxi 3rd level Swashbuckler/1st level fighter though. It is very tempting to go for that Action Surge...