@squid You should probably refer to this thread. MyPaint version pre-alpha preview
Thanks to developer CandyFace, Pencil2D’s current brush engine will be replaced with the MyPaint brush engine in the foreseeable future.
AFAIK that engine has most of the capabilities you ask.
Regarding the canvas size, Pencil2D is different than most drawing software. What you change is not the size of the canvas, but the camera frame size that looks over the canvas (which is theoretically infinite; this depends on your PC specs tho)
To change it double click over the camera layer (yellow layer) we have a guide for understanding the camera here: [Guide] Understanding the Camera Layer
Pencil2D only works with a pixel-aspect ratio of 1:1 (square pixels) The resolution aspect ratio depends on the pixel size you set by yourself (e.g 1920x1080 > 16:9)
A preset feature for new files will be added to the upcoming version of Pencil2D and will be found for configuration in the menu Edit > Preferences > Files Category > Startup Settings Section
These Presets will save various settings, and even though we are still testing them, probably the most important for you is indeed camera size and variable layer types and amounts e.g Like you can have 3 bitmap layers starting up instead of the vector + bitmap, though you always need to have at least 1 camera layer though. This way you can always have one of your custom presets work as the default created file when you press File > New File
Thank you for your interest 