Does running an OpenVPN server and a NAS (samba) server on the same OS instance make the NAS vulnerable?

So I want to make my NAS (samba file server running on Ubuntu Server 18.04lts) accessible through a VPN, and OpenVPN seems the most straight forward way to do it.

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Here are the main questions I have:

• Do I need to virtualize both servers seperately, with VM level disk encryption, to prevent any kind of vulnerabilities?
• Are there any concerns having open ports to the web for the OpenVPN server in the same environment as the NAS I want to protect?
• Should I do mutliple VMs anyway just for good practices' sake?

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Thanks for any advice!