Ok, one thing that contributed to make the planet almost unvisible was the Cloud Layer scale on Planet2, which was so small to cover the whole planet of very light pixels. I disabled it, changed the second sunlight angle, tweaked a little the atmosphere on planet1 (mostly the bluesky parameters).
After that I added a Surface Layer on the second planet, added a very low luminosity coefficient so that the planet surface would pop up a little more.
The planet it's now starting to show up, if you want it more visible, I think the best way is to lower down blue sky settings and choose a lighter sky color to compensate for it. And of course move the sun lights so that it's more properly lit.
Hope this helps, modded project attached.
