New to PowerBI Currently using SSRS for Reporting

Well, there are a lot of questions in there and a lot of nuance to some of them. First, I would recommend that you look at this:

https://www.linkedin.com/pulse/power-bi-licensing-pictures-greg-deckler-microsoft-mvp-

Minimum requirements for Desktop:

• Windows 7 / Windows Server 2008 R2, or later
• .NET 4.5
• Internet Explorer 9 or later
• Memory (RAM): At least 1 GB available, 1.5 GB or more recommended.
• Display: At least 1440x900 or 1600x900 (16:9) recommended. Lower resolutions such as 1024x768 or 1280x800 are not recommended, as certain controls (such as closing the startup screen) display beyond those resolutions.
• Windows Display settings: If your display settings are set to change the size of text, apps, and other items to more than 100%, you may not be able to see certain dialogs that must be closed or responded to in order to proceed using Power BI Desktop. If you encounter this issue, check your Display settings by going to Settings > System > Display in Windows, and use the slider to return display settings to 100%.
• CPU: 1 gigahertz (GHz) or faster x86- or x64-bit processor recommended.

Minimum requirements for Power BI Report Server

https://docs.microsoft.com/en-us/power-bi/report-server/system-requirements

You don't have to use the Report Server but the you would be using the Service unless you want to pass PBIX files around and in that case you would need Internet connectivity.

Note that with Report Server, you need to use a specific, special version of the Desktop client called Power BI Desktop RS.

For 10-20 users, you would just go with Pro licensing. The break point is like 550 for Premium to make sense. See this article:

https://www.linkedin.com/pulse/power-bi-tableau-licensing-deconstructed-compared-greg/