Neat! Glad to hear
Yeah they’ve done a good job with their documentation.
I was tempted by it several times already to try some features I didn’t even consider using.

Yup.
Tailscale has some documentation about it, and also a bunch of examples (And apparently one specific to Immich).

Since you already got some replies, a bit of a different approach would be to set those services up using Docker and having Tailscale as a sidecar to each one of those.
You will then be able to access each one as a seperate device. immich.*.ts.net etc.

Just be aware that for a period of time the MX 500 had many reports of high failure rate. Not sure if it was due to a change of components or firmware.
Example post about it: https://www.reddit.com/r/sysadmin/comments/whr5ek/crucial_mx500_historically_good_recent_batches/
An article (In Portuguese).
And another post about it.