Yes and no. You can store them in a free cloud account, provided you have local copies; there’s a risk your access to the cloud storage could be denied. A security risk is that they could harvest these databases, and decrypt them later.

I think your best bet, if you were to use free services, is to delete old databases from the cloud. Encrypt the new databases with the updated password manager and a new master password.

No. It’s safer to install Windows and Linux/GNU on separate disks. Whatever you do, install Windows first, Linux second.

127 TB of data in the env? That’s a lot

Mullvad has an option in the settings to enable their own DNS filters.