Thanks for sharing your photos. Looking at the pictures, there are a number of obvious changes made to the NGG-16s on the Welsh Highlands Railway.
One of the more obvious changes is the removal of the running board - mounted turbo generator and the electric headlights, replaced on the WHR with small battery powered lamps. (SAR photo on Umzinto - Donnybrook line)
Then there is the removal of the swing seat from the cab, here enjoyed by driver R. Deacon on the Port Shepstone - Harding line in Natal
And of course the couplings are entirely different, as seen here at the Umzinto locomotive shed
The scenery on the WHR is beautiful. The Natal narrow gauges had their own unique charm with Rondavel huts, forests, fields and winding tracks in the hill country