If Iowa defeats Wisconsin, and is 6-2, and if Northwestern defeats Illinois, Northwestern isthe Big Ten West conference champion at 5-1;
and, if Iowa defeats Wisconsin, and Illinois defeats Northwestern and Northwestern is the Big Ten West champion at 5-2, then,
Ohio State would only care about wanting to play in the championship game, if it fears Iowa more than Northwestern. I don't think it makes a hoot bit of difference because if Ohio State defeats either team they are in the CFP, and Ohio State will have little care about whether it is the COVID-19 Big Ten Champion for 2020.
If Iowa and Northwestern both lose to their rivals this Saturday, it will be disappointing for the Big Ten Conference because Ohio State will be playing in a championship, or 2nd place game against what will appear to be much lesser opponent. Overall, I think it matters very little who Ohio State plays in cross-over week. Ohio State will be heavily favored.
I suspect Iowa has developed somewhat better than Northwestern at this point in the season, and would be a modestly more worthy opponent, but my suspicion can very easily be overcome in rivalry week. Wisconsin cast a hex on Iowa several years ago.