Two basic questions about initial setup

Hello, Apologies to ask some two rudimentary questions, but there's no definitive answers that I can find on these topics.

Quick context: We are a company with an Office365 business licence. We've built a data warehouse and we're looking to use Power BI as dashboard tool (alongside SSRS). We want to roll out Power BI to select employees in different departments, as well as obviously a couple of developers. Can anyone help with the following:

1. What version is best to use? Desktop / Web free / Web pro -
I know the difference between what you get with paid vs the free (O365 inclusive) subscriptions, but I'm confused about the Desktop / web difference and how this would affect rollout and what we need it for. Is desktop simply a testing / trail environment?

2. Does our O365 license mean we have to pay for Power BI as they say that the Power BI for Office 365 experience has been deprecated?

Many thanks on helping! Jamie