Hi! If I understand your question correctly and this is about the facetted look once re-meshed, that's expected behaviour with low-poly meshes. The resulting, dense mesh is the same shape as the low-poly just with a higher density, which results in a much more defined shading. To get a smooth surface you will have to apply…
if you use default z brush plane primitive and your target texture is 1x2 you can use 2 and -2 in Array for x axis (using append new button) and 2 and -4 for y axis. Also duplicate the original plane before this overlay scale up. You would be able to use it as a crop factor after you "grab" it , and then texture > crop and…
the trouble usually come from the miss matched normals (when you stitch in the geometry this is not an issue) at the seam. for example.... the cyinder on the right has the normals at the seam edited to be the same as the plane.