Its not a county by county basis its by congressional district. The problem with it is whoever wins the president will almost certainly win the house as well. It sounds great now because it would give the republicans an advantage but down the line it could back fire and give the dems total power for decades.
I dont think the plan will ever fly because of this, it looks just too much like a power grab and nothing else.
It’s pretty clear that Republicans are looking at these changes for political gain, rather than because they make sense as reforms, and voters may not like that. (There’s a reason the GOP is proposing this in blue states they control rather than red states they control, because in the latter case they would be losing electoral votes.)