Hi 25HD, thanks for buying the tool!
I haven't tested Mesh Edit on Unity 2019 yet, so I can't say for sure.
When you export the mesh as an .obj file, are you importing it back into Unity or opening it in an external editor? When you export as an .obj file, the material is saved as a separate .mtl file and the texture is copied to the same folder as long as "Copy textures on export" is checked. You have to apply the texture through Tile Edit mode though, manually selected textures won't be exported. As long as all the files are together that should work in both cases, but it might be different in Unity 2019 (2018 and 2017 should be fine though).
Vertex colours only appear on a model if the shader being used can process them, they should still be applied to the model, but they won't appear unless you've applied an appropriate shader. Also, just as a side note, vertex colours aren't saved when exporting to .obj files.
I hadn't considered the WASD controls for camera movement, there's no option to ignore the shortcuts either but I'll be sure to fix that in the next version when it comes out.
I hope that clears things up, feel free to let me know if you're still having issues with it.
Also, posting here is fine! Thanks a bunch for the kind words, I'd love to see what you make with the tool!