My controversial opinion is that there isn’t much difference between walking and running. In fact, I can give examples when walking can be faster than running.

(I am a reasonably fast runner BTW. Still, I never hesitate to walk)

I think an Apple watch would be your best bet. Modern Apple watches are pretty competent running watches and have top notch GPS accuracy, especially if you get an Apple Ultra watch. A few higher end Garmin watches also have ECG support but I don’t know if that includes Afib detection.

Strava has group runs feature that I highly recommend. It allows to preview the run route, which is a plus.

Once you join a local Strava club, some of them post invites for local runs. At least 3 of the local clubs that I am a member of do that regularly. Alternatively, you can create your own group run and invite all other club members.