In PSC, will we know ratings for each axis?

In a nutshell, almost certainly not (by default) unfortunately :(

We got the individual axis ratings back when I started at Meta, but about a year before I left, they stopped doing that and we were supposed to only get the aggregate rating. Given that companies tend to hide information when it comes to performance (both for interviews and for employees), I doubt that the policy has reverted since I left.

However, if you have a good relationship with your manager, you can probably get the breakdown. I got along great with my manager after this change hit, so effectively nothing happened for me: I still got my ratings breakdown across the 4 SWE performance axes.

Knowing how you did across Engineering Excellence/Impact/Direction/People is very important information, especially as you progress from E4 -> E5 and beyond due to all the axes becoming more important (E3 -> E4 is like 80% Eng Excellence). It helps make your plan to get to the next level clearer.

As for the "sub-ratings" (e.g. EE-/EE/EE+), I don't think those were ever shared on PSC. However, like before, you should be able to get these from your manager if you have a good relationship and you are both comfortable being very transparent with one another.

You can ask for the rating breakdown with something like, "I would like to get a clearer picture of where I need to improve - Can you share the exact ratings I got across each axis?"

If anyone here is currently at Meta, and I'm completely wrong, please let me know!

Generally, your manager won't volunteer this info, but here's a tactic you can try to get some of that feedback.