If someone has access to your computer and your operating system user account, yes. it’s in the keychain of the OS and your OS user account.
It is also possible to just remove the PIN via editing a .json file in the config dir.
When I think about it. The PIN is just handwaving and pretty much useless.
the decrypted files cache, when you opened files? never
yes, it’s all in the same Anytype preferences directory
I would say it’s not an app for total anonymity and security. It delivers a reasonable amount of security with the premise that you have ownership of your devices. If this is not given, Anytype is accessible for anyone who can access your computer’s account. Even if you have a PIN.