Great question. When I hear people I think that’s used to draw attention to common relevant traits “people of England” for example. Persons is more a group of less related individuals or at least with less relevant similarities “persons of interest” for example
Words brought into English can use English pluralisations, so you’re not wrong if you say octopuses. I think Grammar Girl had a take on this maybe 7 or even 8 years ago by now. These days, I can’t see myself getting worked up about it for the sheer fun of being pedantic like I used to.
It’s not octopuses that octopodes corrects, it’s octopi. Octopi is a Latin pluralization, and since the word is Greek and us to i isn’t specifically American, I agree with you that octopuses is fine but not that octopi is fine.