os:elementary OS 5.1 Hera
In elementary OS only the Super key can be used eighter to see the System keyboard shortcuts(by default) or to launch the applications menu. There is no easy and troubleless way to set different functionalities then these because the Super key is used for core OS functionalities like seeing all applications, multispace view, by default Super+Space opens the applications menu for example. As you have already found, you can change the keyboard layout shortcut by using System Settings > Keyboard > Layout > Switch Layout and use only the options there.
The way the elementary OS is built is that you do not have so many options that you can change, if you want to change something because you found it more usefull but it is not implemented into an option - the best way is to post an request issue into https://www.github.com/elementary and if the dev team find a reason to do what you want, they will when they have the time to do it. Sometimes people do some hacks to achieve things, but usually they do not work so well, sometimes they do but it is not for a long, because if the dev team do not give you some option usually the reason is because it will lead to a conflict later because they have some other plans to use it for something else but it is not implemented in the public version of the os yet.