I like to duplicate my video, and make that layer blurry and darker. I then put it behind as a backdrop.
1) Is there a function doing this automatically?
2) Furthermore, I was wondering how could I make it possible so that the main video has a boundry when it comes to width (so that I can zoom in without the video leaving these boundries), but still letting the video in the back show? Sort of like having two video projects on top of each other where one is 1920x1080 and the other 800x1080 ect. Tried creating two 0% opacity masks on the top and bottom but didn't work?
1) You can do some things to make it easier for you, but to have it literally be a one-click and done situation you'd have to create a Macro for that. You can do that with some input devices that allow the creation of macros, or a software like AutoHotKey. Aside from that, what I would do is just duplicate the video (you can do this for all the videos at once in the timeline) and then have a preset that scales up and blurs them, which you can also drop onto all the videos at once.
2) What you are talking about here is called a "Track Matte." You can use the effect Track Matte Key to accomplish this, where you'd point your video to the Matte, which is basically a rectangle defining the area you want to restrict the video to. You can actually do this with the Essential Graphics Panel as well. The Track Matte Key can be a bit quirky in Premiere, and the main thing I would say is that if you're going to be scaling up and moving the clip around "behind the matte," you need to use the Transform effect or Offset effect to do that. Otherwise you'll see right away that adjusting the clip's Motion properties as you normally would also moves the Track Matte, which somewhat defeats the purpose. This is because the Motion effects are applied last in Premiere, so you're moving the image after it has been cropped by the Track Matte.