The planets are moons surrounding a gas giant (she is the personification) according to TFR setting. In the modpack I use Advanced Rocketry because it has so much more customizable space compared to GC/GS. You can configure the sizes, masses, orbital radius, atmosphere color, fog color, etc. for a planet.
Just that I don’t know how to use GT ore generation for a customized planet. So I used Custom Ore Gen mod XD