In my desktop with a Radeon RX570, there where no other steps required.
I just installed these packages:
And both vaapi and vdpau works fine, any good video player can use them. For Intel graphics, libva-intel-driver package needed but it can be installed with the others, they did not conflict at all. The package intel-media-driver may needed for newer Intel chips, but we did not have that package.
nouveau users may need the nouveau-fw package, but we did not have that. But Nvidia driver users have the needed nvidia-utils package installed with the main nvidia driver.
So yes, installing these packages are enough. Then VLC, SMplayer and MVP will be able to use the proper hw acceleration by default.
If you have working internet connection. In a perfect world…
I will do it tomorow.