Assuming Trump gets impeached, Pence will likely be regarded as Ford 2.0 and would lose but by a larger margin.
I'm being generous on Iowa and North Carolina. Both could easily be picked up by Biden. Pence doesn't have that fire that appeals to the working class that Trump and Bernie have. He's another Mitt Romney and George Bush.
I agree, though he’s more to the right and therefore less electable than Mitt Romney and Bush the older (or did you mean W by “George Bush”?). But I agree that he would lose to Biden.
However, the margin would, in my judgement, also depend on the point of time Pence assumes office (how much time is left in the ongoing term). If the president is impeached, the sooner the better for his successor. In JFK’s case for example, it helped LBJ that the assasination took place late in the administration.