Regarding peak years, one point I typically make is that the absolute elite wunderkids, who were bossing the biggest matches as teenagers, is very often they peak at a younger age compared to 'normal' players. Players like Owen didn't reach 27 years old and be massively better than he was at 18, Messi was already extremely good at age 24-25 (91 goals in 2012, it's not like he was banging in 110+ at 27), etc etc Like say a typical player is at maybe 80% of their peak at age 21, the ones that are already really good by that age are probably at more like 90% capacity by then and hit their peak or very close to it by 25. They actually improve less proportionally compared to average players and don't get a huge upgrade in their late-20s.
You get players that do flourish and become much better at age 27-28 compared to early 20s, but very few of them were elite as teenagers like Mbappe / Messi / Owen / Rooney / real Ronaldo etc.
In summary what I'm trying to say is the players that are really good very young like Mbappe don't mature in the same way as normal players, it's like they have a much steeper skill:age curve in their early years and then it flattens out a lot compared to the smoother improvement you see for a lot of players.