Calculating Exact Map Size

OMG, i will have to take the Rorschach inkblot psychological test for this, I guess I will see only quads and components. Anyway I have landscape mad in 3ds max 1,5x1,5 km and have 200x200 quads. I tried to use meshed landscape in UE but than I cant use paint on landscape and that is essential to me right now. So I have to render to texture height map but WHAT RESOLUTION? What I dont get is correlation between quads and components, if I make one component with 256 quads it is same as 2 components with 127 (although resolution is smaller by one) what does it impact on performance (lets say they are same in resolution). also 1x1 and 2x2 sections per component i really dont get it you now separate component in half so i can use 2x2 with 127 quads and have same as first two ? So what number of quads and components and sections to use now (what is better for visual and what for performance)? So i used 256x256 quads (have no idea why) with 1x1 section (also no idea) with 6x6 components (i like 6x6 :D) and got overall resolution 1531 x 1531. So if i render height map 1500 x 1500 pixepls png file it will have 31 meter on every side left like nothing happen ? or i will render 1550x1550 pixels and it will crop 19 meters on each side? can somebody tell me formula for calculating height map pixel size to solve this once and forever?

I think this is the answer to my question although i still doesnt understand relation between quads and components. So my 1500x1500 meter landscape is 1500x1500 pixels png. file?