Like with most technology, init should be based on use-case.
Some setups are not made for quick reboots and that’s ok. When all your container does is run ddclient you might find that even cron can work just as well as systemd.timers
It’s still a misuse of the word - if your software needs testing it’s not a candidate you would release unless you’re a multi-billion gaming company or Cisco
That’s not too easy methinks. You get kvm vm-s though gui/shell/api with proxmox, but no docker (they use lxc). Unless you set up a podman or similar inside it.
Other than that I’d say go with a xen (xcp-ng). Proxmox or esxi host, and spin up a vm as docker host.
I ditched docker in my latest setup, just running 2 machines in a proxmox cluster. I like lxc - as it’s got the footprint of docker and behaves like a vm
That’s an even worse idea imo. If you’re not very familiar with bcd and grub you will find it hard to boot into Linux once windows decides to “fix the boot issue”.
Better to have a separate drive so you can select by picking boot device on startup.
I know it’s possible to dual boot, but it will be some issues at some point