If it were actual VMs, it would be a huge waste of resources. That’s really the purpose of containers. It’s functionally similar to running a separate VM specific to every application, except you’re not actually virtualizing an entire system like you are with a VM. Containers are actually very lightweight. So much so, that if you have 10 apps that all require database backends, it’s common practice to just run 10 separate database containers.
I believe all of these are actually just running Debian as the actual OS underneath, but they give you a webui that makes deploying apps easier.
Of these three, I like the look of Cosmos the most. Seems to be security focused and comes with a reverse proxy and a built in SSO solutions. That’s something that’s usually a pain in the ass to set up yourself.
There’s technically that stupid ass LTT OS but I’m purposely leaving that one out.