Why is there overlapping content?

I don't think that is really a fair assessment of the material. All of the courses are made to be viewed as standalone courses, so there needs to be a bit of background on some of the foundations (like mutable arrays) incase someone didn't follow the track or is coming back to the course after not coding for a while. The tracks are made to string together courses in the same subject, to help provide a basic framework for beginners to follow along and learn as the get more proficient with the material. The overlapping of foundations, helps re-enforce those foundations.

Not using literals in the videos shouldn't affect you at all. I've gone through almost every iOS course, and my code never looks exactly like their code. I follow along typing out every bit of code (I don't download project files unless I'm trying to debug something that I can't find on my own) and whenever possible I use literals and convince methods instead of writing out the longhand formats. Thats part of the beauty of treehouse, because there is not formal style requirements for your code, you can write it however you want.

And lastly, don't forget that you're not the only treehouse customer. Some people take longer to learn, and others (seemingly like yourself) pick up the material a lot faster. They are trying to reach a middle ground with the course content and so far they seem to be doing good job of that.