They do advertise direct export, but I’m not sure if that means encrypted json

Proton does this as well, you can use it completely offline without an account

Well, swanstation doesn’t work standalone and some people have said it performs worse, but it’s not like you need a very powerful system anyway

AFAIK retroarch uses swanstation, a hard fork specifically for retroarch created in 2024 when duckstation switched from GPL to a source available license. Also retroarch alternatively has the beetle core which is also a pretty good ps1 emulator