JoJo's is an obvious example, spending the first two parts being about kung fu vampires and then suddenly gaining iconic kung fu snowflake ghosts.
Having read everything except Vento Aureo and JoJolion now I would agree for the most part.
Speaking of which, Steel Ball Run on its own evolves through the story. I think it's probably my favorite JoJo now. Because it ran for so long and it's when the manga switched to monthly, you get to see a notable increase in art quality around volume 3-4. Some people dislike Araki's new "glamour pose" art style that started developing around Stone Ocean or Vento Aureo possibly, but I think it's alright. Getting back on point, SBR's story feels a lot more dynamic throughout. It starts off very focused on the race, but after the monthly switch it becomes more about what each character is striving for in that race, and even though the main characters are Gyro and Johnny, you get to see a lot of cool interactions between other characters and even get their backstories too. It also probably has the best antagonist besides Kira in my opinion, and they go through a
radical redesign in their appearance as the series progresses.