Funny you should ask. I just listened to a podcast with an interview with Swen, and that came up.
https://www.usgamer.net/articles/ax...-on-baldurs-gate-3s-early-access-releaseSkip to 26:15 for the start of Swen's interview, but the pertinent question is at 33:30. Swen claims that the backstory for the custom character has as much depth as that of any Origin character. At 36:00 he says that the "Who do you dream of" character is a pretty important character, key to the custom character.
Man... This got me a bit worried. I'm gonna discover my own characters story while playing and I don't know it although it supposedly happened to me? They need to be pretty damn careful how they go about this or it could really f up a lot of peoples characters...
As to what the OP says... I dunno man. I generally prefer to have a fairly clean slate character. Baldur's Gate 1 is one of my all time favorite RPG's and that is mostly due to the great structure and freedom of play it gives. The ONLY thing I don't like is the very set up of us being a kid, LITERALLY a kid regardless of how we make our characters in the creator that let's you pick portraits for old men etc... I mean obviously we are a bhaalspawn and that could have been perfectly well conveyed without making us kids barely of age. Really limiting. BG2 start is a hundred times worse with setting up a whole GOOD friggin canonical party for the first game... And even though there is relative freedom in the city it never felt like a wonderful open world like the first game did. Probably why I never finished the second game... I think BG3 sets up a pretty good starting point with pretty much any type of character being viable... Although the dialogue options available in early access still aren't quite varied enough for my taste...