Depending on the origin we follow, Shuri really doesn't have the same backstory at all. Hudlins version she never meets T'Chaka, and the latest rise/ other version she is just a small child so her memories will be pretty vague. Maybe slightly more compelling than Hudlins but not much all the same. Her best showings were under Hickman where she truly felt different for. T'Challa, unfortunately she has been a parasite ever since and they regressed her development.
Tosin... Kinda. His backstory is still pretty basic and just copied version of the Jabari except they use in the mystical sense. But it's no different than the Jabari, except they are somehow bigger smug a**holes with no sense of appreciation for ehere they reside sbdbhoe lucky theybarnrthst the golden coty has protected them fornalk this time.
He had the chance to be shown as a misguided but we'll intentioned new hero and instead has been shown as a toxic, nationalist, fake oppressed POS who needs to DESPERATELY get checked... HARD. First by a villain (physically) then by T'Challa (morally) then maybe he can be used after that