selectively permanently muting some attendees but not others

While it is possible to do so, webinars may be what you are looking for. Here is our article with a Meeting and webinar comparison.

You could do this in a regular meeting by starting a meeting, going into the Security options using the bottom ribbon, then disabling Unmute Themselves and Start Video under the Allow participants to: header. This will disable all participants from speaking or turning on their video, you can then selectively choose others within the meeting to elevate to co-host in the participants page; co-hosts are able to bypass these restrictions and use their camera and unmute.

This also comes with the downside of giving a wide range of controls to many users in your meeting by giving them co-host privileges. I'd recommend checking out Roles in a meeting to see if you are alright with giving these users co-host before doing this.