I followed the recommendation of choosing threads, memory consumption and the number of iterations (in that order) on my machine. But now I wonder which passwords (by means of entropy) are actually secured by this set of parameters.
Clearly, a single letter is not secure, regardless of the parameters; but on the other hand, using a 256-bit entropy password renders the usage of argon2 pointless. So the security of my hash certainly depends on the relation between password strength and argon2 parameters. Since I am using old and not powerful hardware I am concerned, that the time it takes for me to calculate the hash is negligible for a large scale attacker. (This might be even worse for hashing on mobile phones or embedded devices.)
So the question is: Given a certain set of argon2 parameters, what is the minimal entropy a password should have so that the hash can be assumed to be secure?
Alternatively: Given a certain set of argon2 parameters, how many passwords can the fastest supercomputer available today (in 10/20/50 year) check in a second?
Edit: I am using a strong (>= 128-bit) password for locking my password manager, but entering this several times is tedious. So I thought using a key file that is protected by a simpler password. Since I am syncing stuff to the cloud, the hash of the simpler password can not be considered a secret. In order too choose a simpler password that is still considered secure, I need to be able to estimate the protection gain from using a strong KDF (e.g. argon2).
Edit 2: This question and answer tackle my question in a general context (not Argon2 specific) very well.