Also, speaking of TRAPPIST-1:
Last night I made an addon with my imagination of the TR-1 system. I used data from www.trappist.one
which had estimated masses and densities for most of the system. Most of these planets' masses are poorly constrained at present, so for now it's really anyone's guess!
I will gladly explain my reasoning for the presentation of each planet here, if there is interest. In general, I considered that a magnetic field is necessary to the retention of substantial atmosphere; furthermore, that a planet needs a) a (semi-)molten core and b) a relatively fast rotation to maintain a significant magnetic field. While I have considered the TR-1 planets are hypothesized to be tidally-locked, I also noted that some studies suggest a planet can avoid tidal locking in the presence of a substantial hydrosphere and relatively flat ocean floor (thus decoupling the planet's solid surface from its liquid surface, such that only the ocean itself is tidally locked).