What is the best screen size for Character Animator

In Encoder, make sure you change from output to Apple 422. Better resolution. And also, you can change the size of the Character Animator aspect ratio. 
Click once on your "scene" in the "project" box (top left). Look at your "properties" box (on right) under >Scene. Click on "Scene". You'll see Frame Rate, Duration, Width, and Height. Change the width and height to the aspect ratio of 3,840 px, by 2,260. And you're done! Now go to your menu, Scene, New Scene Camera, and adjust the camera's x, y, and z position. You can zoom in too. 

I think question number one is what screen resolution do you want your target video to support. I was not sure, so I picked 1080p (1920x1080). My theory was it looks better to downscale an image rather than upscale, and lots of laptop screens are 1080p. So I went with a resolution that matches most laptops. If you use 1280x720 and upscale to 1920x1080 (full screen size of a laptop) you can expect some minor bluriness I guess (but would not have thought too bad). If you have a higher res monitor (mine is double 1080p I think), then you will be scaling the video 3 or 4 times up, which I am guessing would get noticeably blurry.

Having said that, 720p is not *bad* - most YouTube videos are probably that resolution or lower. Its just if you view on your own monitor that is higher resolution, it won’t look as good. So you need to understand where you are going to show the video. E.g. in a class room with a super high res monitor? Or via a lower res projector onto a screen? Etc.

Next you need to understand the resolution of your artwork. I went with Illustrator to avoid worrying about this - vector artwork scales more easily. If using PSD files (raster files), the resolution will matter. If the artwork is lower resolution, then higher resolution video won’t help. You need to understand the resolution of the artwork and how big you scale it up to on the screen. E.g. if you scale your puppet twice as big (200%), then you need double the resolution of the puppet to make it look good.

But all of the above is not related to puppets going off the edge of the screen. That is fixed by first setting the resolution of the scene (in the properties panel) - I always use 1920x1080 - then you scale the backgrounds and puppets to correctly fit into the scene window (as per the other thread). I frequently pick “fit” for the scene zoom factor, then zoom out a bit from there (using ALT + mouse wheel) so I can see the surronding out of camera content. With the background image, this is also how you can make sure you have not left a black border around the background because its smaller than the video content area (which from the other thread was the problem you just encountered). Because I drag hands etc of puppets that start out of camera view, I need to see where the hand is off camera to start the drag correctly, which is the other reason I often zoom out a bit.

So the resolution of the scene/video, the resolution of the puppet, and the scale factor you apply to puppets all matter - but you have control over them all. The biggest problem is if you get a PSD file that was created with too low a resolution for the scale factor you want.

Note: There is also a “render as vector” option if you have AI files (not PSD files). That may help as well. I create my AI files with 6000pt height and “high resolution” in the document properties, and have never had to resort to that option. The problem with it is some Illustrator features (such as gradients) don’t work in “render as vector” mode. So I just cranked all the settings up in Illustrator, then never had to think about it again. (Mind you, I don’t know if my rendering speed went down as a result!!!)

I hope that helps!