Every Isekai protagonist is replaced by the following characters from the beginning of their series:

1) Ichigo Kurosaki (Bleach)

2) Monkey D. Luffy (One Piece)

3) Izuku "Deku" Midoriya (My Hero Academia)

4) Saitama (One Punch Man)

5) Vegeta (Dragon Ball Super)

6) Arale (Dr. Slump)

Each of these characters have their own powers in addition to the abilities of the various Isekai protags (provided that they would end up in the same situations where the original protagonists got their abilities). How would each of them handle the trials and tribulations of the various Isekai universes?

Bonus: How well would a Composite Isekai Protagonist do in each of their replacements' respective universes?