Power bi embed with RLS

Hello guys! I'm still a newbie in power bi been developing a dashboard for a client for a year now and its going well. Recently we have talked about the possible deployment of our dashboard which will include RLS since we expect to introduce our solution to external users.

Currently the expected flow is SQL -> Power Bi -> RLS. Now I have explored on secure embed with RLS i have already tested it via the microsoft github playground to use the parameter username() to trigger the RLS.

But my question is for me to test this further would i need to develop a web app then generate the token within the app and pass the user variable for the RLS? Do you have any sample practical applications? What if the current website of my client is not coded in C#, python (could be wordpress) is there a way to use this for our current site without me having to dissect the website? Any practical applications?

Lastly, i understand there are possible charges that we might be paying specially if we opt for the dedicated capacity but is there a way around this?

What we have right now is a Powerbi Pro license.

Thanks so much guys for the replies