Hi Julie!
If you’ve scheduled the release, it won’t show up in the catalog (or some other widgets) until that day. But if an enrollment date is in the future and the content is released, the learner can see it in the catalog, but they can’t enroll until the enrollment date. (They are different functions that are independent of each other.)
Releasing means to be visible in the catalog, where enrollment is for allowing actual enrollment.
I don’t think changing dates will be an issue, especially if the date is in the future.
Hope that helps but as always, I love seeing what others advise that I might be overlooking. :)
Thank you so much for this helpful response @amberkleven