Final answer:
The most impactful plan for Georgia's freedmen was General Sherman's Special Field Order No. 15; however, the later overturning of land grants and political changes impeded its long-term success.
Step-by-step explanation:
The plan that arguably had the greatest impact on the freedmen in Georgia was General William T. Sherman's Special Field Order No. 15, which intended to distribute land to freedmen. However, President Andrew Johnson's nullification of this order and the return of land to the original owners severely limited the potential benefits it could have had on the freedmen's economic independence and societal status. The initial promise of land grants could have given the freedmen the resources needed to protect themselves and prosper post-Civil War. The Sea Islands experiment provided a brief glimpse of this potential.
Additionally, the involvement of the government in ousting conservative ex-Confederates in Georgia in 1870, followed by Democrats regaining control, showcased the political volatility of the period. The federal government's failure to sustain its support for freedmen’s rights led to erosion of their gains, illustrating the difficulties in ensuring a successful transition to freedom.