Ways to deploy Web/Database servers at one Hardware

What I have

I need to release some Inner Service in one organization:

• backend: Python

• database: MS SQL Server (or maybe Postgres)

In this task I'm restricting with one server having 16 cpu, and 16 Gb ram.

In my plan here would be:

1. Web-server: Web-application on it should handle about 30 users at one time

2. Database-server: Should contain multiple databases that would be used by described Web-application

Surely it's not advisable to have the database- and web-server on the same machine as it can leads to security, scalability and performance problems.

What I need

I need to partition server's performance. So:

1. Do I need to use virtualization and is it only one approach to this problem?

2. If I would apply virtualization, what OS should be better for having such hardware configuration (should it be Hypervisor on Windows or VMWare/VirtualBox on Ubuntu)?

3. What is percentage ratio that I should to part my hardware for Web/Database?