EndeavorOS;
Gives the benefit of having latest up-to-date packages for gaming, while negating the downsides of having to configure the OS or graphics driver upon installation.
Honestly, if think EndeavorOS comes with full UI support to download stuff from AUR and Flathub, I think it would become a pretty solid OS for any casual user looking to get into Linux. (Well, unless they are religiously against Arch. Then again your casual user probably don’t even know what ‘Arch’ is or care enough to be religious about it.)
Also yea, usually you run Ubuntu LTS or Debian Stable on servers unless your company paid for some licensing.
I personally use Debian. For your case, you can install lightweight desktop environments such as XFCE.
Honestly from my point of view after reading your post, you don’t have a terminal or operating system issue, it feels like you are new to self-hosting and don’t know how to start configuring from scratch.
Ideally you want to look for documentations or keep asking for online help. For example, with installing docker, you would want to refer to this: https://docs.docker.com/engine/install/. Welcome to system admin life, where you spend more time reading/understanding than configuring.
Personally, you can even use AI Chatbot to help you with stuff, just be specific on the system you are on, the goal you are trying to achieve and the problem you are tring to solve.
Which brings me to answer your next point about CasaOS: It exists so that you can skip most of the ‘system admin life’ step. It skips almost all the setup you would have needed to do on a fresh machine, and just leaves configurations. The downside is usually it eats up more resources than a self-configured install since it comes with redundant features you are unlikely to use.
TLDR; Pre-configured OS such as CasaOS is a solid choice if you just want to set it up and be done with it. If you are here to really learn about system admin stuff, then pick any of the Linux Operating system (Debian-derivatives recommended) with a lightweight DE.
Happy self hosting :v