Luka Rejec has an interesting post on “quantum characters” as a solution to the character-customization-vs-speed-of-creation conundrum. Basically, the idea is that you can have mechanically complex characters and still get started quickly if you just sketch out a general concept at start of play, and only define the granular bits and bobs when they come up in play.
This method is explicitly called out in Fate, though it is not the “default.” It’s my preferred Fate character creation method, though. However, I’ve never seen it employed in any other ttrpg. Does anyone know of other ttrpgs that officially support “quantum” character creation, or have you used the method as a tool in systems that don’t officially endorse it?