I’ve never used Portainer, but does it have an option to only notify of available updates?
For things that I don’t mind breaking, I use latest. For the services that matter, use a specific version. Take Immich for example, in the 2-3 months I’ve kept it running, there’s been 3 breaking changes that would prevent startup after update without manual intervention. Immich is an extreme though, some other projects have been working fine with latest without touching them for years.
I follow the important projects’ releases (subacribe if possible), and update manually when they publish an image with a new version. I’d see it as either updating manually and being OK about possibly being a version behind every now and then, or using latest+auto updates and being OK with waking up to broken services every now and then. Which might never happen.
I’m very much biased towards Podman, but from what I understand rootless Docker is a bit of an afterthought, while Podman has been developed from the ground up with rootless in mind. That should be reason enough.
The very few things Docker can do that Podman struggles a bit with are stuff that usually involves mounting the Docker socket in the container or other stupid things. Since you care about security, you wouldn’t do that anyway. Not to mention there’s also rootful Podman, when you need that level of access.
I’d recommend an RPM-based distro with Podman, the few times I’ve tried Podman on a deb distro, there’s always been something wonky. It’s been a while, though.