I am very partial to Autodesk Sketchbook itself, because it fits how my brain works. At any given time it may or may not use a subscription model, though; it can't make up its mind. Seriously, it's free-as-in-beer right now, so do pick it up to play with it.
RIGHT NOW, there's 1 day left on a Humble Bundle that includes Corel Painter and Paint Shop Pro if you pay a little more: https://www.humblebundle.com/software/painter-create-with-confidence
My Spouse says its brush model is better than Sketchbook's and it's reasonably fast now. /2