One thing that is clear from listening to Mike Pence is that he is very happy to talk immigration. I’m not a huge fan of Trump’s immigration stance, but at least it has the virtue (from a communications perspective) of drawing a sharp contrast with the Democrats. Trump and Pence already have all the negatives that go with being immigration hardliners, they may as well embrace it and peel off every vote that comes with that.
As for Kaine, he clearly relishes talking about problems specific to Trump – his boorishness, his insults, etc. That’s all to be expected, but it also illustrates how desperately the Democrats needed Trump this election cycle to save them from near-certain defeat.