JCandeias, slight misinterpretation going on here. What the research team found with their computational methods is that there may be distinct boundaries on the PV diagram where supercritical CO2 changes from "gas-like" to "liquid-like" behavior. I.e. small change in temperature or pressure will cause dramatic change in whether the fluid behaves more like liquid or gas. This is not the same as saying that there is a distinct interface, as seen between actual liquid and gas phases. So no obvious shorelines and sea surfaces as on Earth. Definition of supercritical fluid is that this interface disappears (because the density change approaches zero), as seen in the video demonstration.
It's not so easy to wrap one's head about planet-sized consequences of that. For instance, if slight changes in pressure and temperature lead to dramatic changes in behaviour, there should still be boundaries because in planets substances aren't pure and the kind and amount of impurities is affected by the properties of the stuff those impurities are in. But those boundaries would likely be subtle and probably pretty unstable, very easily affected or disrupted by turbulence. I guess you'd be able to see them if you can see far enough (like up to the horizon, or something like that), but at short ranges they'd be very hard to or even impossible to see.
So no familiar landscapes, no. And probably no Mars-like landscapes either, except in areas above supercritical levels. Which means such planets would indeed look different from how SE is showing them.
Or maybe I'm still missing something.