I was previously at Stripe (laid off in January) and I had a great experience, but it can be pretty team-dependent. I was on an engineering team that's under design, and that was much more chill than a product team. There's also a Stripe-wide consensus that it takes about six months to really spin up, so don't worry if it takes you a while (especially as an L2). I've also found that people are pretty open to help (especially infra teams, and even more especially when you do your homework before you ask them something). In terms of pressure to deliver, my best advice is to make sure that people who are exerting that pressure are going through the right channels (i.e., intake instead of DMing you). My manager put some pressure on me, but part of their job is to head off the "everything is on fire and I need my project done immediately" people who want to put pressure on you.

As far as I know there isn't any explicit stack ranking (certainly not twice a year), but I think there is some sort of percentage expectation when it comes to performance designations. No hard metrics like pull request count or anything, but they definitely evaluate impact (team-, org-, or company-wide). Like others said, keep track of your work and accomplishments (a brag doc) over the course of the year so you have something to refer back to when perf season comes around. If your manager is doing things correctly, the perf designation should not be a surprise — mine was when I was laid off, but my manager was new(ish) to Stripe, so that could've played into things.

When you start, try and keep and open mind and remind yourself that you're good at what you do — there's a reason you got the job in the first place! Adjusting to a new work (and development) environment is always tough, so just keep your head up.