Assuming proplyds in 4d are large groups of objects with random orbits then there is an effect able to create planets with long-term stability. A major problem in 4d is that because of the dropoff of gravity (the inverse cube law) a planet would need extremely low eccentricity for said stability. If you have 2 objects with the same eccentricity and (from a top-down view) the periastron and apastron align and they collide, the eccentricities cancel out.
Over a lot of imperfect collisions local deviations smooth out and you’re left with a high stability system of planets in nearly perfect circular orbits. Not all systems will reach this and 66% will fail to be stable. This means that free-floating planets will be much more common.