a] with a systemd service on a headless device , it may be preferable to start it on boot and keep it running rather than only running during an interactive login session. Among other things, this helps prevent a *race condition* that may occur when socket activation fails to initialize audio devices in time for their first use, leading to one-time errors after reboots
b] til #spawning tmux is managed by systemd even if its a user service
when is a #systmd job or service or #linux user session supposed to linger is matter of how a service depends on the other *or not*
moreover some of these may have their own user accounts like rootless containers , with their own namespaces , which need be mapped to other services like #vpn
one can always check it with systemctl --user or linctl
so #podman has this runRoot directory: "/run/user/1000/containers" graphRoot directory
tbc