There were conflicting ways with which Lucas tried to reconcile making Anakin and Vader the same person (I don’t say this in a negative way; I think is the best creative decision in all of Star Wars, personally).
In Ben’s monologue to Luke in SW77/ANH, he describes Anakin as if he’s a peer, and Vader as “a young Jedi” and his pupil.
I think the idea is that, when the characters were combined for ESB and ROTJ, it was retconned so that Vader and Ben were closer in age. As said in ROTJ, Anakin was still his student, but they became peers after Anakin became a knight.
I think there’s a slightly noticeable shift in Vader’s portrayal between ANH and ESB in making him appear more “mature”. He’s more stoic, his voice is deeper, and he moves in a more deliberate fashion. I think that’s a result of Vader, behind the scenes, going from being just Ben’s former pupil, separated by decades in age, to his former friend, around the same age, as well as being a father. This is solidified by Anakin’s unmasked self and Force ghost in 1983 being a similar age to Ben.
When it came time for the Prequels, it seemed that Lucas changed his mind and went back to the idea that Anakin/Vader is noticeably younger then Obi-Wan, leaning more towards his description as a young Jedi. The Prequels establish that he was only 22 upon turning to the dark side, when Obi-Wan was 38. This is what led to the Force ghost change. I’m sure Lucas handwaves his rough appearance when unmasked to being roasted by lava (I prefer the idea of dark side physical corruption).
I think a middle ground is better. Anakin should’ve been more in his late twenties when turning, with Vader being in his 50s in the OT. 22 is just too young. But I don’t think Vader should be like, in his 70s in the OT either.