When vault is locked should I be able to see and read files "IMPORTANT", "masterkey" and "masterkey....bkup

Yes, that’s normal and no only with these files no one is able to decrypt your files. See here:

Ps: you can just delete the important file. It only contains information about where you have to store your files so they will be encrypted properly. Means: this is just an generally important information how to use Cryptomator.

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