Keyboard -> Keyboard shortcuts from Settings will show all the available keyboard shortcuts. You can also create your own custom keybindings
These seem like a lot of personal design complaints rather than actual issues with GNOME itself.
And to my understanding Gnome expects you to use basically every application with a full screen window anyway
You misunderstood, that's not what GNOME expects at all. Your app not maximizing on startup is because the app doesn't maximize on startup. GNOME doesn't have a setting to maximize all apps by default since that should be the app's responsibility.
If you want the auto-tiling window manager experience, you'll need to install an extension (Paperwm, tiling shell, Forge, Pop shell). Extensions are like applications, there's no shame in using them.