Rate limits for profile info (from the public player profile endpoint) for multiple users in a row?

For example, if I had a list of 1000 players, and i wanted to get the stats for all 1000 to ultimately find who has the highest amount of followers, or to see how many out of the 1000 are streamers.

I would have to make 1000 requests to the pub/player/{username} endpoint.

Would I encounter any rate limits? If not, what if the list is even larger, lets say for 300000 users?

I've done some testing for 100ish users at once and found no issues other than some loading times but I'm unsure whether I should test a larger amount of users. Also curious if different rate limits are applied to different endpoints (I also want to make requests to the user stats endpoint for ratings).
Thanks for the help!

That's explained in the documentation.

https://www.chess.com/announcements/view/published-data-api#pubapi-general-rate-limits

I've read that but since I understand just a surface level of developer lingo, I can't figure out if what I'm doing is going to be rate limited.

If I'm not doing parallel requests but I'm doing them within a short amount of time, one right after the other, it'll be fine?

Based on the documentation and what I tested, yes. If not parallel you should be fine. (although it can be a bit slow...)

Up the requests and find out  
You're right in that according to the API documentation, serial (sequential) access is unlimited.
Rate limits can be set at the application level and have global reach on all endpoints or set for a specific endpoint. Given that no rate limits are specified for any individual endpoint in the documentation, it's probably safe to assume no endpoint would differ from another in this regard.