Whoever gets that link can browse it in a web browser.
I've used this to share albums of photos with gatherings of folks; it works very well. It does assume you have your Immich installation publicly available, however. (Not open to the public, but on a publicly accessible web server)
it’s not a fair comparison with Google because Google has a much bigger target on their back. There are millions of users of Google, so the value of hacking Google is very high. The value of hacking a random Immich instance is extremely low.
Setup immich VM or docker container with a cloudflare tunnel
Front access with Cloudflare Access (ZeroTrust) for free.
Set "can only be accessed by users with email = xyz@myuser”
Done.
Now assuming this is the same user email as the one you shared photos with, there is a base level of security keeping the riffraff away.
Home IP is never exposed either, because it's proxied through the cf tunnel.
I keep that running on a VPS, but with with proper firewalling you could probably run it on the same machine.