Yeah, it's really not very difficult :) 128 unit high wall, using a 512 pixel high texture means the ratio is 512:128 You can divide this down (128 goes into 512 4 times) to get 4:1.
Thats a good point, I saw Hero Forge uses 512 & 256 for each of there characters so I assumed in a FPS 512 would be ok, for 3rd person 256/ 128. I'll just forget about Mobile & stay with 512
Quick Follow up for the texture maps i used. I use 1x 1024 Diffuse and 1 x 1024 Normal, 5 x 512 Diffuse Map, 5 x 512 Normal Map and 1 x 512 Specular map