I want a gaming device but also a device which I could “replace” my PC with for some basic stuff we all do on windows.
Like watching videos on YouTube, Netflix. Installing any app I need, installing mods. Installing adblockers.
Maybe do some MS office work and write/view documents etc.
Is that possible while staying on SteamOS? Or this operating system only meant to be used for gaming with steam launcher?
You can do all that in the SteamOS desktop mode. I’d definitely recommend keeping your keyboard, mouse, and monitor though and perhaps a dock. With MS Office, open-source software exists that is mostly compatible with Office files.