There is a lot of software written for the iPad for art due to the iPad having the Apple Pencil. Here I will add some advice, tips, tricks and tutorials for the software I use the most.
I used Affinity Designer first, because I had this on my PC, but I wanted to sketch and decided to try Procreate and found this as good art software. As time goes by I will use other software, and add information about those as well.