It depends on you and your budget.
If you enjoy coding and would like to learn how to code - then you're looking at Godot, GameMaker, Unity.
If you don't enjoy coding and would like to make games without it, you'd get further with Clickteam Fusion, Construct and GameSalad.
There are more than 30 game development engines listed on itch.io & if you ask "us" - well we all have opinions and they're all different, in the end it's not really going to help you.
I'm not familiar with the games you mention or RPG. But in general, things in games are just coded in, they're not necessarily extensions. However, many of the game development software have stores and you can purchase examples, tutorials and guides on how to create what you want. They also have many free tutorials.
I'd suggest as a start to play around with the different software engines - see which ones you like, don't like, work through their tutorials until you click with one of them.