Covington (Newton Co.) and Madison (Morgan Co.) do not require emissions testing.
"Vehicle emissions testing is required annually in the 13 metro Atlanta counties in Georgia (Cherokee, Clayton, Cobb, Coweta, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnett, Henry, Paulding and Rockdale County) in order for motorists to complete their vehicle registration."
Tax system changed for new registrations in 2013. I have a '99 Jeep under old system and a '15 Jeep under new system. All pull behind trailers are subject to annual ad valorum tax (not affected by new tax law). I just paid $141 annual tax (plus $12 tag fee) for my 20 footer valued at $8k. Our rate here in Union County in $17.6 per $1000 value. Taxation value is 40% of actual value.