Aseprite does not have full support for pens, so all a pen does is act as a way to move your cursor. There’s no support for pressure, tilt, or any other tablet features.
Because of this, using a stylus isn’t that useful in Aseprite. It’s faster for doodling and rough line sketches, but slower for precision work.
I use a Wacom Intuos tablet, but when I want to do loose sketches or block stuff in, I prefer to work in other software with pressure support, since then I can work more more fluidly and quickly than in Aseprite. I find it quicker to import my sketches into Aseprite than to have to change brush size manually while sketching.
For pixel art beyond the sketch phase, I don’t usually use the pen at all, I find it much more efficient to use the mouse.