How do you manage larger projects?

Hi all,

I have tried a couple engines and wanted some more insight before choosing one.

I have a couple of questions relating to medium/large projects:
Note these are my personal feelings and more than likely misunderstandings of common concepts in gamedev as opposed to what I am accustom to with webdev

1) How do you handle GDScript spiraling out of control?
Context: What I mean by this is, as I come from a strongly typed world TS, Rust, etc. how do you guard against brittle access once you change something? This is the same reason why I tried Love2D (Loved the framework) but lua being dynamically typed meant as you prototype and progress at a rapid rate if something changes but is not accessed due to being interpreted you only get to the crash once it reaches that segment
2) Is it worth considering C++/C# rather than GDScript and how does this affect the iteration speed?
3) How do you handle multi interface inheritance?
Context: In Unity you'd often create a bunch of interfaces and compile them as needed e.g
For an area which damages units youd maybe do something like this for the script:
- MonoBehavior
- IArea
- IPropertyModifier
- - ModifyProperty<T,U>(U prop, T source)
So if you also had say some destructible environment elements, characters or anything which required some sort of property to modify we could invoke it based on what the trigger from IArea would return.

Thanks again :)