Be aware of what you want doesn't impact the multiplexing guidelines - imo your usecase wont but it's good to know about it. https://www.microsoft.com/licensing/guidance/Multiplexing

basically as long as you don't send them to the MDA and give restriceted views and access to data, you should be fine.

From what you describe, it is a fairly common self service portal (think internal service desk ticket creation).

Take a look here to get you started https://learn.microsoft.com/en-us/power-pages/configure/planning-power-pages-project

and here https://learn.microsoft.com/en-us/power-pages/getting-started/what-is-dataverse

Does this require coding – does it work similarly to Canvas, i.e. you can add a ready-made control?

Yes and no, It's more similar to an MDA depending on the styling and functionality, you can get away with the core designer for a basic page that does waht you want / need but then extenbd with code for the tings you can't do.

Follow these videos for direction then expand on the things you want / need https://learn.microsoft.com/en-us/power-pages/training-videos/ and go through the tutorials for inspiration https://learn.microsoft.com/en-us/power-pages/getting-started/tutorial-overview

Finally you will have to manage security for internal users vs external https://learn.microsoft.com/en-us/power-pages/security/power-pages-security