Three thoughts for Part A: First, if there are any competitive Republican primaries like a contested state legislative seat, I would think you would not get many cross-over voters in those areas. Those look to be more confined to the north side of the county. However, I don't think there are any contested Republican primaries for county offices, so it would make sense for those people to cross over to influence the outcomes (if they are that motivated to do so). However, to point 2) you need to have Republican voters who are willing to pull a Democratic ballot. Some purist Republicans could not bring themselves to pull a different ballot and may be telling themselves that the Republican candidate for DA will win. Additionally, point 3) is that you would need to have voters who are opposed to Fani Willis so much that they are willing to vote for Christian Wise Smith. It seems he is running to Willis's left, which is not how you usually get crossover voters (see Republicans voting for Hank Johnson over Cynthia McKinney or Democrats voting for Nikki Haley over Donald Trump - you need a candidate more moderate or a candidate you can stomach). Part B: probably not.

electing a more progressive fulton county DA in an ill-fated attempt to save their own Presidential nominee from RICO charges is truly the best way for Republicans to make america great again