The unfortunate truth is that this totally depends on the field and how ambitious you are within that field. Community radiology means just do some sweet hobbies and get great evals. Mid tier academic anesthesia or general surgery means some quality research, particularly required in a pass/fail boards world. Beyond boards (p/f for you; rip), any quantity of research is going to be important to keep doors open. Worry about quality later as opportunity presents itself. Get pubs where you can. It's easy to talk about quality from an MD student perspective but means almost nothing from a DO student perspective when research is much more of a luck and "get what you can" scenario for almost every DO student. Number of pubs is far more important because there isn't a real scenario where you are turning down a bunch of projects to find a really good one. That's just no reality IMO. Just do what you can by working to find chances and rolling with it if it looks productive.
As far as the original question, hobbies that you truly enjoy and can speak about for 5 minutes passionately are important for any field. Do not discount this. No one wants to be in a program with some robot. Anything that looks like premed volunteering is pointless and unnecessary unless applying to some bleeding heart FM programs, frankly. Psych is a unique case because early commitment to the field is shown through mental health advocacy (and can actually make a difference unlike all this other BS like FM soup kitchen resume fillers).
Try to get a leadership position, teaching position, and mentorship position if at all possible. You can usually kill two birds with one stone with these positions too on your resume. This comes up in all fields.
Finally, this could be debated by others, but I feel that a lot of students think that step going p/f is going to mean volunteering and other premed things are now important. DO schools already push this stuff for some reason and will do so even more now. They try to tell their students not to worry about academics as much because programs want to see all kinds of dumb **** like volunteering and being on 4 club committees. It's like a built in excuse for underperforming academically for the school. This idea is just plain not true though IMO. Programs' number 1 objective is finding people with academic competency and superiority. This did not change with p/f step 1. It just got a lot harder to find a new metric and easier for people at good schools. There is just a search for new metrics. Step 2 and clinical evals (lol) are now way more important. Some may argue preclinical grades will factor in more but I doubt it. Basically, I'm saying don't go out doing premed things and overloading the schedule with clubs and whatever because it isn't going to help like some people think. The goal should still be focusing on the medicine.