@rbt: I think Cavill's Superman would be portrayed as weaker. The filmmakers were mindful to portray Cavill's Superman as a toned down version in contrast to previous film versions. By contrast the CW versions are embracing the comicbook power levels more than the DCEU version.
As to how the crossover will actually show them, I'd say you're probably right. However it depends on how much screen time Welling will get. It's looking more and more likely that he will just get a cameo and not do much.
As to Routhman's age, if they are taking inspiration from Kingdom Come then he should be far more powerful than the others. KC Superman is 3-4x more powerful than the regular Post Crisis Superman and straight up makes him look like a joke. Judging from the way they have aged Routh up, he looks to be in his 50s, whereas the film version was supposed to be late 20s/early 30s.