Biden (or any other Dem) gains nothing if Trump loses a red state. The Democrat must get 272 electoral votes, and s/he must get them in swing states and blue states. If the Dems write off a red state, it makes no difference whether Trump or Cheney wins it.

There is no prize for winning a plurality of EC votes. If the Democrat doesn't win 270 electoral college votes, the election goes to the House, where each state has one vote, decided, as best I can make out, by majority vote of the delegation, although I'm not sure what authority exists for that outcome. At last count, that algorithm favored the Republicans. Whether the delegations would hold for Trump, however, is another matter. The Congress in question is the new Congress, so we don't really know how that would play out. BTW, the Senate elects the Vice President if there is no majority in the EC. So we could end up with a President and Vice President of very different stripe.