That's why you always practice 3-2-1 with important data.

My photos are on: Captured devices(phones, camera). Immich on my homelab, and google photo(which is lossy, but better than nothing).

The issue with this is that Google gets a copy of your photos. If you really want to use Google or other cloud storage, you should encrypt your files.

Proton Drive may work better here?

I am honestly not sure. I use GG photo because that what i use first and i was too lazy to investigate better deal. Also, i know Google does really well at keeping my data available, which is what you want for backup.

One mistake with your google account and poof, everything is gone.

Granted, an average person most likely will never mess up, but in google-land the surface area where to make that mistake is quite large.

Luckily i have 321 back up, don't i ?

I didn't check ToS of proton drive, but in my experience, every cloud storage has requirement about what kind of data is allowed to store(after all, they dont want to accidentally store illegal stuff).