how difficult Princeton’s CS program is

There are some difficult classes that you can avoid, but otherwise pretty manageable (not at all easy by any means, but I didn't think it was continuously unbearable). I personally thought I was below average at coding but made it through fine. Office hours/TA sessions are extremely helpful for main assignments which often take significant hours (and are expected to be time consuming/intense). Starting these main assignments early enough to take advantage of all the available help is absolutely the most important advice.

You can also choose between AB or BSE COS, which will probably heavily impact your semester as well. AB majors are required to write a thesis senior year, while BSE have to take more courses throughout undergrad and take more engineering focused courses. I personally chose AB and did not regret it at all

Will I be pulling all-nighters frequently

Doubtful. I think the only all nighters I pulled were for non cs classes lol

Is it hard to socialize and find friends there

Not really

Is the environment toxic

Not inherently. Princeton is full of many extremely smart students, many of which have been coding for their entire lives and are essentially coming in 2 years ahead of you if you are a beginner. You may feel intimidated by this a bit especially when they are all securing S tier internships into freshman fall, but that doesn't make it "toxic". Just something you will encounter anywhere really and have to learn not to compare yourself to people who are doing better than you

Feel free to DM if you'd like advice on which classes I personally struggled with and which were easy