I noticed that you can change the bit rates for the FFmpegs and so on if you want to render in a video instantly. Is there any way to do it for pngs?
PNG is not a lossy format like jpeg. It can vary the file size just with compression quality. Think of it as a zip packer. The more you set compression level, the more time it takes to compress, but the more compact file it produces, but after unpacking a file is the same. The compression level you can change in the output settings. Also PNG can be with or without alpha channel (RGBA / RGB). And also you can save 8 bit or 16 bit per channel color depth. So, if you render to PNG, it's like rendering to bitmaps (BMP) and then compress them with zip. No quality degradation on any settings. Just time and file size - that's what you can play with.