What canvas size should I use for Photoshop files in which I create digital art? To me, it should be a size so that it won't easily become pixelated. I would also like for it to be fit for all devices meaning that it shouldn't become pixelated viewed on such devices. Don't we all want that? In that case, what size should I use? For example, if you have a size of the now common 1920x1080px, you would need to scale it a whole lot if used on retina devices. That would lead to loss of quality from the resulting scaled version, which is sad when you spent so much time creating art. What size do you use and why?
4K displays are becoming quite common these days and most 4K TV can display image files. I do not think 5K and 8K displays will see wide spread use on computers because of their cost and they require a special high price display adapter or two display adaptors. So you may want to consider canvas size like 38640px x 2160px and 2160px x 3840pd a wide 16:9 landscape aspect ratio and a tall 9:16 portrait aspect ratio. These will also print around 13"x7" at a 300dpi resolution. The down side is the file will be larger and your paint application performance may suffer some.
Large size 4K TV DPI resolution is not as high as you may think a 70" 4k TV resolution is around 63dpi. My 55" 4k TV resolution is 80DPI. My 24" 4K display resolution is 185DPI. A 14.69" 4K display would have a 300dpi resolution 12.8" x 7.2" image size.
I always think and design for print . As stated above, this may affect perfomance, but thats the nature of the beast. You can always size down finished artwork for digital display but always keeping a version for print.