Add-ons (now apps) can't be done without HAOS. It's one of those non-obvious things.
There's other things I forget which are also more difficult/annoying to manage on the container version.
I have a rather large docker compose stack so my first experiments with HA were as running it there.
That lasted maybe a week before I went and ran it as a VM instead.
Yeah, I ended up buying a dedicated mini PC ($100 refurb) to install HAOS on. HA is pretty much useless without being able to run add-ons. I run everything on k8s in my home server, I don't have a VM system set up and didn't want to bother just for HA. It's funny, the pattern of a central application that uses docker containers to add plugins seems like a perfect fit for a Kubernetes Operator. I suppose it still misses out on some of the advantages of running everything "on metal" for integrating with physical components like USB dongles.
Apps/add-ons is just another container, so you can add them manually in the compose file.
Yep, I run esphome in a separate stack w/o issues.