Stage 7 of the Hong Kong Trail – from Tai Tam to To Tei Wan – gets you down towards Cape D’Ag; at end, a flight of steps up to the road. Much of it about dead level, alongside a catchwater.
Don’t think there’s level option other than road to get closer to the Cape itself – and access to southern tip restricted as must pass thro communications base. There’s also a fairly level trail winding along west slopes of Dragon’s Back. One way onto it is from near Tai Tam Road: steps or winding road up past correctional facility, then south along stage 8 of HK Trail. Instead of keeping to the HK Trail as it turns up to D Back, keep straight on, along the more level trail (tho maybe at end, have some steps to go down).