The "best editor" will always depend on your particular needs. For quick, almost "back-of-the-envelope" computations, I use plain R, but when I want to code something complex or want to develop a package, I turn to RStudio. I specially like how it integrates with knitr / Sweave and how easy it is to generate new versions of a package.
Cannot give you any feedback on Tinn-R, but as always with these questions, try both and see which one is best for your needs.
Definitely, R Studio. I have not tried anything else. Also, feel no need to do so. R Studio has everything that I can think of and much more than that.
More interface you will use, then, it will decrease efficiency, the speed and also, by doing so, you will never understand the real efficient speed of any programming language. Also, if you want to increase cybersecurity in your work and want to understand it in future regarding any programming language, use it from terminal. Once, you are quite efficient one should use it directly from terminal, never look for creating piles of unnecessary interfaces of using it through another things like GUI.