Hello, I'm no expert but I'll say a few things about your posts:
Issue 1: I didn't see anything about sudo in your comments. Are you running the driver install as sudo (root privileged user). For further advice on this issue, you will need to provide more information as to where you downloaded the package from and the exact steps you took. Also any troubleshooting you may have done already. There is the "Hardware Configuration" tool that may provide more information or let you know what drivers you have installed. I think it has the same info as running the sudo mhwd -li --pcicommand. You may need to post your inxi -Fxxxaz also just in case.
Issue 2: I'm not sure on this one. I don't run games on Linux currently. However, I would leave that one for last because if you are having driver issues, it may be related.
Issue 3: If you look for "Add/Remove Software" in your menu, that is the GUI packet manager that runs pacman in the background. Pacman is a CLI tool only and it has GUI interfaces. A note about Linux in general, most tools are CLI based first. All of the commands I mentioned above are CLI. Garuda developers have done a great job at integrating GUI apps in to the interface but for the dirty business, you will need to go in to the CLI a lot of times. It is similar in Windows how a lot of configurations are not available unless you go in to the registry. I would recommend finding a terminal text editor that you like, there are plenty (shot-out to nvim but I don't recommend for beginner use). When you have to pop open the hood on Linux, it usually involves the CLI.
Issue 4: Not sure, Deluge is a gtk3 app which is a different window manager than KDE. It should be supported but there may be some extra libraries that you will need to install to get it to work. It may not look as good as the native KDE GUI apps.
Issue 5: I think this is set in the Appearance or Window Decorations settings. You would probably need to change themes to change the behavior. Also I don't want to mess up my desktop so I'm not going to mess with it but you could right click on the panel and click Edit Dock. Move pointer over to the App Menu section and a pop up with a line circle settings should come up. You may be able to modify how the app menu behaves there. I turned a few things on/off but nothing changed. Maybe you need to log out and back in to take effect. Not sure why it says it is broken.
On a different note, Linux is like working on a hot-rod. You are always under the hood and some issue will come up here and there. I've been working with Linux for quite a few years and still the learning curve is steep. As previously mentioned, Garuda is cool in that it tries to make the jump easier but there are some things that just don't change when it comes to Linux in general. What I find frustrating is that it is disjointed and a lot of wasted effort goes in to reinventing the wheel even within the Linux community. Hence all of the window managers and disjointed tools/drivers etc. Good luck!