It's good that you list specific game references. Two of them were made with Unity, but I don't know about Sara is Missing. Besides the tools, I'd also try to find out how many people worked for the project and how long, which is why the first thing I do when I play a game is check the credits, and I like reading the postmortem articles on gamasutra (I guess I should read the ones on itch.io too!) This way you can get some realistic expectations on the resources needed and whether you need to adjust the scope.
Back to game engines, you probably won't go wrong with Unity since it's so popular, general purpose, and cross-platform, and there are a lot of free and paid addons. But by the same token there's a lot to learn. If you're new to gamedev and especially programming and you're interested in visual novels, for example, then I'd suggest starting with something like ren'py which will let you concentrate more on content and get in the gamedev flow more quickly, and then you can work your way around to other engines for other projects as appropriate. I haven't used ren'py for anything but I recently saw a game here, I think it was Distortion Nation, which had some nice animation and graphics (including UI) which I didn't know was feasible in ren'py.