Limitations of modding tools?

I want to get into game development as a game designer, thus i’m learning UE4 to try to make mods.

What I’m wondering is, what cant I do in the mod tools, that game devs can do in the normal UE4 engine.

I’m assuming modders cant change the core UE4 engine code

What about networking related to lag compensation/client side etc?(eg if i want to choose between lag compensation or clientside for diffrent mechanics.)

From what I’ve seen in the ark modding tools, we can add almost any sort of art assets? any exceptions?

is it possible to do any C++ at all in the modding tools, or full blueprints?
if so, is there anything blueprints cant do?