A little bit of context to keep in mind about PANIC ROOM in 4K: First, it was Fincher who supervised and determined virtually everything about this release, including the remastering.
Second, while I haven't seen the 4K yet myself—distributors often get discs before critics—it seems unlikely that a new film scan was done here. Like ZODIAC, the original 2K DI—which is the finished version of the film—was probably upsampled and used as the basis for new remastering work. (Remember, SE7EN was actually finished on film, not as DI.)
Given that the 2K DI was completed in 2002, it's going to be limited to the state of the art at that time (think the STAR WARS prequels), so improvements over Blu-ray will be modest. Edge enhancement was very common back then. The digital effects were of lower resolution. And any DNR would almost certainly have been applied then, not now. This is simply a case where the film—because of its vintage—can only look so good, thus it's wise to keep your expectations in check.