Med school's tough for sure, in particular the pacing. But it definitely doesn't have to be -- and shouldnt be -- competitive! Part of how competitive the environment is or isn't has to do with the med school but it also has to do with the class. Y'all have to decide, collectively, as a group, that you're going to get through it together and support eachother. Maybe that happens, maybe it doesn't, but it takes effort from every individual to make that happen not just the school. Your class' and school's "culture" is what you make of it. You might also thrive in certain situations, classes, environments where others don't, and vice versa. Try to help eachother out and be there for eachother when you recognize that you are in the luckier group for the moment. It's easier said than done when everyone is pressed for time or stuck in their own lane, but it's a good ideal to strive for. More likely than not, you will find your closer support network pretty quickly and that will obviously help too.
The approach to learning in med school is just different than in UG. You are learning a lot of things very shallowly and very quickly as opposed to a smaller number of things quite deeply as you did in UG (or a very small number of things extremely deeply if you've been to grad school). The content also never goes away. Accept that you will never be done learning physiology, although your command of it and what is actually practical and important for you will certainly change. The same concepts come back over and over at different angles depending on how you're curriculum is structured / what you're taking at the time. Personally, I like the pancake metaphor a lot better than the firehose one. The only thing medical school asks you to do is eat 5 pancakes every day. No big deal right? Not really! But!...you have to eat 5 pancakes every single day, and if you eat just 4 pancakes one day then the next you have to eat 6. If, god forbid, you fast for one day then you'll have 10 pancakes to eat the next day, etc. This old metaphor seems almost prophetic in the Anki era of medical education.
I'd say I'm less stressed *about school* than I was in UG because overall I feel pretty good about being able to Pass and I also know that at my school even if I don't pass it's definitely not the end of the world. It's nice to not have to aim for the maximum score on every exam. My sources of stress are simply keeping up, because falling behind means more pain later (pancakes etc.) and more existential (i.e. deciding what kind of doctor I want to be, actually learning medicine, trying to be intentional about finding good role models in medicine and becoming a great physician for patients, a good scientist, and not just a great Step 1 score, etc.)