You will have to make the decision ahead of time, yes! Once a character is in Hadriel, they would not be able to be canon updated with CRAU memories. They can come in with them, but they can't be added later.

If you CRAU from a game with physical changes, you would have a choice - your character could come in without the physical changes but with the memories, or they could come in with the physical changes and make an IC deal with the gods to get their old bodies back, if that's what they want. Basically, it would be up to you as a player whether you wanted to simply wipe the changes completely, play out an IC fix, or have them indefinitely. However, if you're apping into a cast that already has castmates in Hadriel, we'd request that you talk to them before you chose to keep any physical changes.