Then I’d say use re_formula = NA (the default for marginal_effects, right?), i.e. Panel A, because these will not include the uncertainty from the county/region levels. Panel B would answer the question of what marginal effects could look like in a new, not previously seen county/region.
In cases like this I think it helps to spell out the mathematical model to grasp the implications of those choices. (Also, you should probably think about the conditions of the marginal effect and see if those make sense. Here you need domain expertise, so I won’t be able to help with this.)
Hope this helps (at least my first paragraph, haha)!
Cheers,
Max
PS: You need to fix your plot axis’ labels ;)