It’s almost the same as plain Android, only with the Google services removed or locked down, and additional security restrictions and permissions control. Most apps work without any additional configuration, unless they’re doing something unusual.
The only supported devices are Pixels, so take your pick from the list: https://grapheneos.org/faq#supported-devices
The article is blogspam, it restates the SciTechDaily article, but with fewer details.
The original article just says “salt water”, so I assume sodium chloride as well, which means it’s probably not useful for most food products. The original paper might have more details, but I’m not bothered enough to try getting it while on my phone.