OpenCart: Why are some modules editable and some not (only enable or disable)?

Question

CMS

The second day I deal with OpenCart. I can edit some modules, write everything necessary in HTML, etc. In the settings of other modules, there is no such possibility, you can only enable or disable it. Need to go somewhere in the files?
There is no access to the files yet, they gave me a theme already stretched on the engine and said that access to the admin panel would be enough for me.
PS: I wandered into the section with templates, everything is done there on the twig template engine, where are the variables for this template engine defined?

Answer 1

I wandered into the section with templates, everything is done there on the twig template engine, where are the variables for this template engine defined?

In controllers, but without access to files, this information will not help you

Answer 2

Some modules may have multiple instances of themselves, some may not (not always necessary). Why so - so the developer of the module decided.