If you really want to use them, I'd recommend the dkms drivers we have in OBS https://en.opensuse.org/SDB:NVIDIA_the_hard_way#Further_read...
And yes, I believe if you want you can install with sysvinit, though we are primarily a systemd distribution first (with extensive sysvinit compatibility.. people still love those runlevels)
Ts'o has a interesting use case for runlevels that didn't translate well to systemd.
He set up a runlevel on his laptop that was the same as the graphical one, except it stopped various daemons etc to keep battery drain low. He would then switch to said runlevel when he would be away from a socket for an extended period.
When he tried to translate that to systemd, he ended up with all kinds of side effects. One of them being that he lost access to the Fn combos, so he could no longer control the screen brightness etc.
As far as I can see the x11-video-nvidia package in the page you linked has quite an old nvidia driver version for Tumbleweed - https://software.opensuse.org/package/x11-video-nvidia
Again I might be missing something, and in practice it might be easy to install the latest drivers, but this is a bit off putting. I don't know the details of how your build system works or why it keeping up with Nvidia drivers complicated, but this seems like it'd be quite a fundamental thing for a lot of users. The vast majority of people who play games on Linux are going to want recent proprietary Nvidia drivers, so having that as a footnote at the bottom of an article that says it's not recommended/supported doesn't inspire confidence.
Still, I'm intrigued enough to give it a try.
There is a second "openSUSE Tumbleweed" under the "unsupported distributions" category, and that has the more up to date nvidia packages I'd expect
If someone would like to take a look at the lovely ruby behind software.opensuse.org and fix that bug, I'm sure we'd love the pull requests :) https://github.com/openSUSE/software-o-o