While each company has some unique qualities, my guess is that being an engineer in any of these places would be pretty similar and include:
* A lot of engineers and teams
* Lots of organizational / promo based manuevering and social engineering
* Problems at scale - some technology, but mainly "number of cooks in the kitchen"
* Work which might not be very interesting
* high compensation
My guess is that the OP's concerns would hold true at most of these big tech places that pay top dollar.
* get a CS degree from a top tier program, preferably a PHD
* Pivot in from a normal software job. This is probably only possible if you have a bunch of C++ experience, and some top (FAANG) names on your resume.
I don’t think it’s possible for me to go down a PHD path.
HFT seems like a cool gig if you can get it
I didn't go into the domain because I'm not a big fan of money games. YMMV.