We can just barely sometimes tell the difference between a small neptune, a large earth, an ocean planets, a coteless ocean planet, and a hycean planet. Trying to guage not just habitability but also terraformability is a ways off yet.
We can start with size and surface temperature though. We’re not going to survive on a gas giant, and anything with a four digit temperature is right out.
That would make gravity just wafting farts.
At least we’d know that dark energy comes from some kind of hole.