is nas + backup to amazon glacier a good solution?

For cold / glacial backups, M-disc will run you $200 for 10x 100GB discs, plus around $300 for a pair of USB Blu-ray burners. With that, your data up to 500 GB can be written in duplicates and stored at two physical locations (one drive at each location), with very strong guarantees that it will be readable far into the future.

If you write 2 additional disks per year, this is a $500 initial investment plus $20 per year. Compared to Google's "AI Plus" plan you break even in year 5, assuming Google keeps pricing flat.

Of course you don't get any cloud access or similar.

Yes, but it's hard. I've not found something that works well with glacier, because most backup solutions want to write state, modify files immediately, etc, and glacier can't do that. It would need to be an append-only backup; strictly.

I do a bit of a hybrid. Borg to expensive, always available storage, but really large stuff that rarely changes and is less important, I exclude and manually throw in glacier once a year or so. Think, all your blue-ray rips, etc.

I wouldn’t back up directly to Glacier, because you want to be able to verify your backups, and reading from Glacier is expensive.

Yes. Should have 1 onsite + 1 offsite backup ideally.