Are Cryptomator files stored locally?

I want to store personal files on my work provided OneDrive using Cryptomator.

If I ever lose access to the OneDrive, will my files still be on my computer?

This depends on how you have configured your onedrive sync client. If you have disabled the „files on demand“ feature, or in other words if your files are always synced fully, then the answer is yes. If you have configured your sync client to free up space by locally deleting not recently used files, then the answer is no.

Cryptomator does create all files locally, but it’s the sync client which decides if files stay local or not.

Adding to this: If I want a) some folders to stay local as well and b) some folders to be available online only (i.e., downloaded when needed), do I need to work with 2 separate Cryptomator vaults?

When I have configured a folder to only download on demand, can I free up such space locally again (i.e., make the file available online only again), once the downloaded file is no longer needed locally?

Yes. Because you and your sync client cannot see which unencrypted folder and subfolders are which encrypted vault files. And this has to be configured in your sync client. Means your sync client has to support that this feature can be toggled for separate folders. In onedrive and Google drive you can toggle this only for all synced files (as far as I know)

Also something that depends on your syn client. With onedrive for example (also afaik) you can define to „free up space“. Then onedrive will „delete“ all files not used for equites while from your local disc and keep the online version and a reference.