I've got few docker containered Tailscale deamons as a sidecar, exactly. Those should work as the same host (login based), as in the original home server. I'm mostly unsure, how the whole "VM environment" with attached drive with whole docker engine install will perform - also in terms of connection.

I've got personal laptop + mentioned Dell Wyse 5070. In near future (months) I'm thinking about extending to another home server client.

I know using ansible in that scenario will be somehow harder than direct ssh, but I want mainly to learn the process (for future work possibilities) and have that extended control of the changes on the bare OS.

Moving services one by one could be a solution but required additional networking - currently I've got Tailscale domains for mentioned critical ones (Nextcloud, Matrix) and I thought about running from the same storage could keep the same hostnames of Tailscale nodes (if that even possible). What do you think about that issue?

Currently I've got all of the docker containers defined troguht Portainer Stacks, so I could easily covert it to base docker compose files.

I'm not afraid of that risk and just try to mitigate possible outage of services longer, than expected (I hope to refresh the server in 1 day, but as with everything new, it can take longer).

What do you mean by "direct upgrade"? I want to have every direct modification done on OS to be done troguht ansible playbook on refreshed build, so my assumption is that I have to purge / start from new SSD in that case.

Take a look at this step-by-step tutorial => Tutorial FreeCodeCamp Dual Boot